The memories of the bloody crackdown on Tiananmen Square’s pro-democracy protests 30 years ago are sharpening. Hong Kong is heading down the path of no return, warns Carrie Lam, its chief executive. Beijing’s rhetoric is more threatening still, with an official warning of “terrorism” in the city. China’s state media has shown paramilitary police troop carriers apparently massing in Shenzhen, bordering Hong Kong.

Ten weeks after the protests began in reaction to the anti-extradition bill, the impact is growing, the mood is turning uglier and violence is spiralling. For now, Beijing’s intent still seems to be intimidation, not direct action. Brute force by the People’s Liberation Army or mainland paramilitaries is likely to be its last resort. But hardline language, harsh policing, attacks by thugs and punitive charges have not exhausted activists. They have only inflamed matters.

Tuesday saw a new level of violence at the airport – extraordinary clashes with police, and protesters hitting two suspected undercover officers even as others tried to protect them. Such assaults are unjustifiable and many in Hong Kong – including activists – will rightly revile them. Protests that target symbols of authority have won a remarkable degree of support in a city that once prided itself on its political caution and conservatism. But the airport occupation, which led to the cancellation of hundreds of flights, and especially the attacks there, take the movement into new territory. The astounding backing that protesters have won – with finance professionals, medics, lawyers and even civil servants taking to the streets – could easily fray.

The aggression of some participants has been fuelled not only by the government’s intransigence but by brutal police tactics, including firing tear gas into a metro station, and directly at protesters. A woman may have lost an eye after she was hit in the face, apparently by a beanbag round. The UN human rights office has urged the Hong Kong government to launch an inquiry after reviewing what it calls credible evidence of police employing these kinds of weapons in ways that are prohibited by international norms and standards, “creating a considerable risk of death or serious injury”. The use of undercover police has fuelled suspicion of provocateurs.

Authorities have done their best to stamp protest leadership out in recent years. Two of the founders of the 2014 Occupy movement, academics Chan Kin-man and Benny Tai, are locked up in maximum security prisons for their role; many more activists have served time. Elected legislators have been disqualified. The lessons that many have drawn are that protests are the only way to make themselves heard; that no one should take the lead; and that they are bound to pay heavily for their activism when the protests end. None of these are conducive to an early end to the disorder.

While the leaderless quality of the movement may offer it flexibility and resilience, it also makes it far harder to channel. The protesters are far more sophisticated, politically astute, informed and connected than 1989’s students – they have grown up with a lively civil society and strong traditions of protest and free expression, the very things they want to protect from Beijing’s encroachments. Yet, as in 1989, these protests have developed their own momentum and cannot easily be controlled.

The Communist party does not want to mar the celebrations of its 70th year in power on 1 October. But if protests show no sign of ebbing before then, might it decide that it is better to act sooner rather than later? The demonstrators should give Beijing no excuse for violent suppression. But the behaviour of a small minority does not justify a ruthless response to the movement as a whole. The UK and other governments should remind China of the political and economic costs attached to violent suppression of these protests.