As China attempts to stamp out Hong Kong’s pro-democracy protests, demonstrators have endured tear-gassings and beatings from riot police. There have even been a few deaths during the violent clashes. But one of the most intimidating sights came this weekend: soldiers from mainland China on the streets, dressed in shorts and t-shirts—and armed with brooms.

Video from Channel News Asia, a Singaporean outlet, shows dozens of young men from the People’s Liberation Army clearing the streets of bricks and other debris. Quietly, almost robotically, they disassemble roadblocks built by protestors. The troops carry away fences and chairs.

Victor Ting, a reporter for South China Morning Post, shared a clip of the soldiers returning to their Hong Kong barracks later in the day.

According to the Basic Law (Hong Kong’s mini-constitution), forces stationed by Beijing in the city shouldn’t interfere with local affairs, though officials can ask Beijing for the troops’ help with disaster relief or maintaining public order. A Hong Kong government spokesperson said the soldiers’ assistance this weekend had not been requested, describing it as “purely a voluntary community activity initiated by themselves.” Pro-democracy lawmakers were quick to condemn the move as both a political PR stunt and illegal, warning it might be designed to “gradually rationalize” PLA operations.

As The Telegraph writes, the PLA’s appearance on the streets—its first since the protests began—could “be seen as an incremental raising of the political stakes from Beijing.” Even without guns, it’s a daring show of power and a reminder to all citizens that a crushing repeat of Tiananmen Square could transpire. At present, it’s estimated that there are 12,000 PLA troops in Hong Kong, double the normal number.

Shortly after the PLA soldiers swept the streets, police reportedly moved in on Hong Kong Polytechnic University, where student protestors have constructed catapults and bombs.