Candlelight vigils mourning a Hong Kong student killed in a high fall during a pro-democracy rally have quickly spiralled into violence between protesters and police.

The centre of violence was on Nathan Rd in the Kowloon district of Mong Kok, one of the most densely populated locations in the world, where activists built barricades and trashed an entrance to the metro station.

Police used a robot to detonate a suspected explosive device on a side street following at least three blasts in the area, amid a lengthy stand-off with petrol-bomb throwing protesters on Friday.

Police fired tear gas there and in Tseung Kwan O, to the east of the Kowloon peninsula, where University of Science and Technology (UST) student Chow Tsz-lok fell from the third to the second floor of a parking lot in the early hours of Monday.

The 22-year-old fell as protesters were being dispersed by police.

He died on Friday – graduation day for many students of his university.

Mr Chow’s death is likely to fuel anger at police, who are under pressure over accusations of excessive force as the former British colony grapples with its worst political crisis in decades.

UST students trashed a campus branch of Starbucks, part of a franchise perceived to be pro-Beijing, and rallies are expected across the territory over the weekend.

“Condemn police brutality,” they wrote on the restaurant’s glass wall.

Hundreds of students, most in masks and carrying candles, then lined up in silence at UST to lay white flowers in tribute.

Thousands also left flowers at the spot where Mr Chow fell at the car park, occasionally singing hymns.

In Mong Kok, dozens of activists barricaded off Nathan Rd, which leads to the harbour to the south.

They vandalised a closed metro entrance, throwing in bricks and pouring oil through the metal grill, and destroyed a phone booth in a small explosion.

There were clashes and fires in the New Territories town of Sha Tin.

Mr Chow’s friend and fellow UST student, Ben, 25, said the computer science undergraduate had liked playing netball and basketball.

“We played netball together for a year,” he said through tears. “I hope he can rest in peace. I really miss him.”

Students and young people have been at the forefront of the hundreds of thousands who have taken to the streets since June to seek greater democracy, among other demands.

They are rallying against perceived Chinese meddling in the Asian financial hub.