The following witness account by a German woman was published on the Politically Incorrect blog [in German].  This is an English translation:

After an approximately six hours drive, we (my three passengers and I) arrived in Brussels and went into the metro, to go from the Maelbeek station to the Luxembourg place. In the upper part of the station, policemen stopped a fellow passenger and myself and accused us of wanting to participate in the demonstration. The other two passengers managed to stay unnoticed and escaped the arrest. The policemen stated they would have to take us into administrative custody. The arrest was confirmed by radio. After further inquiry, they explained that the reason for the arrest was the display of the European flag, the black-red-gold colours [German flag, note of the translator] on a sign as well as my Israel flag. The German flag in postcard size, likewise fastened to my backpack, did not attract any attention.

Even longer negotiations with the fortunately predominantly Flemish policemen (the present French speaking policemen, treated my fellow passenger quite rudely), at the metro led to no result. The offer to cover and stow the flag and sign in the backpack and go away, led to nothing. There was no request to leave, no reading of rights, nothing. Consider this: we had not even left the metro at this time, and were neither at the Schuman nor at the Luxembourg place. At least we could convince them not to put handcuffs on us and to mark our personal things, so that they would not get lost.

We went with a prisoner transporter with flashing blue lights from the station to the Palais de Justice. There we had to wait, since the arrival of so many arrestees blew up their capacities. About ten to fifteen minutes later we were requested to leave the transporter and to follow other arrestees. The way led through rows of policemen similarly to a pike alley run. With calls of “faster, faster” we were driven into the cell block. This was already well filled.

I was put into a cell with two older ladies. We introduced ourselves. The older one of the two, about 60 years old, belonged to the demonstrators of the Vlaams Belang (incidentally married to a Brazilian of indian descent, so much for the right-wing extremists racists of the Vlaams) and the other lady, very delicate, about 40-50 years old, elegantly dressed, with a Christian background. Both had been bound during their arrest on the backs with cable straps. Their traces were easily seen on the Christian, her hands were particularly red and were swollen due to the cable straps, they faded only after hours.

I was now separate from my fellow traveler, but I could however still see him in another cell, and communicate with him through shouting. The entire cell block was well filled - hardly a cell (2m x 1,5m), which was not occupied with three to six prisoners. The sound level in the cell block was nearly intolerable. A gang of seven to eight French speaking neo-Nazis shouted speech choirs (most fortunately incomprehensibly for my ears), and struck for hours against the cell doors. The arrested Flemings for their part over-sounded these with Flemish singing or shouting support for their arrested parliamentarians. None of the arrested Flemings showed these neo-Nazis any sympathy. I kept busy myself with the singing of the German national anthem, insulting the neo-Nazis, which were locked up directly opposite to me, and discussions with my co-prisoners. After several hours we were given drinking water (however not for my fellow passenger, despite repeated inquiries) and again one hour later a waffle. The drinking bottles were now used by the neo-Nazis, to make still more noise. The Flemings meanwhile ignored them, as an older gentleman had probably broken down due to stress. I could only observe diagonally through the bars, he lay quite a while on the tiled floor of the lowest floor surrounded by several policeman/law officers, who took care of him. It took still quite a while, about one hour, until finally professional medics arrived. They treated the man with syringes and oxygen. A half hour later he was transportable and they carried him away on a stretcher.

My fellow passenger appeared around half past five at my cell door and told me that he would soon be released. The accompanying policeman or justice official promised to get me released quickly as well. Around six o'clock I was then led out of the cell, searched, interrogated, and put into another cell with young women from the Vlaams Belang. Talking to them I learned, how they were arrested at the Schuman place. Again the smallest and most delicate one of them (about 160 cm tall) was thrown directly by four policemen on the ground, she had to put her hands behind her head and then a policeman knelt over her. Squeezed like this, it took a while before the cable strap was put on. With the other two women, who were in the process of removing their burkas, in order to step on this symbol of suppression with their feet, only two policemen each were probably enough to overwhelm them roughly. Now it meant waiting again. I noticed the fact that their shoe laces were missing and asked the women about it. I was informed that they had to give up all the laces, belts, chains and bra.

I found this very ironic, as I still possessed all of these dangerous items. During none of my body searches, I was requested to get rid of any of those items. This let me to think that this measure was quite arbitrarily enforced. In the meantime I had lost sight of my fellow passenger. In the cells calm had returned, most men - also the neo-Nazis - were released and only the women remained locked up. Gradually they also were released and I sat as the last one in my cell. Briefly before eight o'clock I was also led away. At this time only two women were left with me in the cell block. At a counter I was requested to confirm the receipt of my belongings. I had been searched at the metro and my identity papers, my purse, my pocket knife and my backpack had been taken away. During a second search my remaining items: car keys, change, my stab resistant vest and a hair band where taken. I simply refused to sign as I neither speak sufficient Flemish or French, furthermore some items were still missing.

Then someone brought the things from the second search. Again I refused signing anything. Then finally got I my backpack back. I carefully check everything, until I was sure that nothing was missing. Meanwhile a group of policeman/law officers observed me. For a repeated time this day, when seeing the Israel-flag I was asked whether I was a Jew and why I was carrying this flag with me. Rejection was written in nearly all the faces of the police officers - two of them in the Palais de Justice mumbled something and pointed at the flag. One of them said also something like "Here comes trouble!".

Briefly after eight o'clock I could finally leave the Palais de Justice. At not a single moment I was offered to contact the German Consulate or was given information about my rights. At the stairway the young women of the Vlaams Belang were so kind to have waited for me for me and joined me on the way to the metro. Not a single woman with whom I was locked up spoke negatively about the flag, Israel or the like. However I was given the advice not to show the flag so openly in Brussels, once I would travel alone after transferring in the metro. Naturally I did not heed the recommendation, but I experienced quite fast, why I got this advice.

In the metro I sat on one of the free seats and placed the backpack beside me. The flag of Israel was bound outside to the backpack and I had to raffle it together, so that it did not touch the dirty floor. This awakened the curiosity of two roughly 40-year old men, who by their dress style and language could clearly be identified as Muslim. Unquestioned, one of the men rose and tried to seize the flag at my backpack. I quickly reacted with a strong blow to his fingers and shouted a loud and furious “Finger weg!” (German: "Hands off!") He looked somewhat irritated around (the train was quite well occupied) and then sat then together with a second man on the seats opposite to me and both began to talk to each other in Arab, whereby I several times clearly heard the word “Jahud” (Arab: Jew), while they were smirking at me, I looked furiously back.

At one point they stepped out of the train. Arrived at my stop, I made myself on the way to my car. It had meanwhile become dark, there I run into a frustrated youngster on his motor bike, who at first 'only' switched inconsiderately between footpath and road. He quickly discovered me and drove several rounds around me to probably take a closer look at me. I could not identify him as he wore a helmet. I totally ignored him. When this probably became too boring, he sped away on the sidewalk through pedestrians to finally disappear. Around 9 PM, I met finally my three fellow passengers at my car and we start our way home.