Seething with anger, the black-clad studentshurled gasoline bombs, threw bricks and even aimed flaming arrows at the riot police, who answered with tear-gas volleys and rubber bullets that hurtled into Hong Kong’s university grounds for the first time.

And with those battles on Monday and Tuesday at the territory’s largest universities, another unspoken rule in the antigovernment protests that have been convulsing Hong Kong for six months was shattered: the sanctity of educational campuses from the police.

The clashes turned what had been sanctuaries for the students at the core of the movement into scenes that evoked medieval citadels under siege.

They opened a new chapter that threatens to further disrupt the Asian financial capital, which has struggled for normalcy despite the increasingly violent protests against the Chinese Communist authorities in Beijing who have the last word over Hong Kong’s future.

Hong Kong has fallen into recession as tourists have fled and as its busy shopping areas become backdrops for street battles between demonstrators and police officers. The world is asking hard questions about what could befall Hong Kong as Beijing further tightens control over a city that is supposed to operate under its own laws.