The Chinese military issued an unprecedented warning amid another night of chaos and violence in Hong Kong on Sunday, as masked protesters risked tear gas and arrest to march in defiance of an emergency ban on face coverings.

As the initially peaceful mass protest on Hong Kong island and in Kowloon spiralled into violent clashes with riot police, the Chinese People’s Liberation Army warned protesters they could be arrested for targeting its barracks with laser lights.

The warning, the first of its kind during four months of escalating unrest in the global financial hub, was displayed on a yellow flag as hundreds of demonstrators shone laser pens at troops in fatigues. The soldiers responded with spotlights as they filmed the scene.

The nearby Kowloon Tong metro station was trashed, its windows smashed into tiny pieces. The entire mass transit rail system, which has been targeted by protesters who believe it has colluded with the government and police against them, was suspended on Sunday evening.

Wildcat protests sprang up and disappeared quickly around the city as bands of protesters played a game of cat and mouse with the riot police.

The most radical among them threw Molotov cocktails at advancing officers, who responded with tear gas and arrests. A journalist was struck on the head, briefly setting his helmet on fire.