Belgian soldiers patrol at the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)

A Belgian soldier patrols at the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)

A pedestrian walks past a police car at the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)

A Belgian soldier patrols at the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)

Belgian police guard at an entrance of the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)

Belgian police patrol at the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)

A Belgian soldier patrols at the Christmas market in downtown Brussels, capital of Belgium, Nov. 27, 2015. Brussels' Christmas market opened here on Friday with high security measures. (Xinhua/Ye Pingfan)