Turkish police have fired water cannon and tear gas near Taksim Square in Istanbul during a protest triggered by the funeral of a teenage boy wounded in anti-government clashes last year.
Earlier, tens of thousands of mourners chanted anti-government slogans as his coffin was carried through the streets.
Clashes have also broken out in the capital, Ankara, and the city of Izmir.
Berkin Elvan, 15, spent nine months in a coma after being hit by a tear gas canister as he went to buy bread.
His death on Tuesday triggered violent protests in at least 32 towns and cities across the country - reminiscent of last year's unrest.
Many of the protesters echoed his mother's assertion that Turkish Prime Minister Recep Tayyip Erdogan was to blame for the boy's death.
As tension rose, Mr Erdogan again appealed for calm, urging his opponents to express their opinions peacefully in local elections later this month.
"Whatever issue you do have, solve them in polls on March 30," he said.
Earlier, crowds holding pictures of the teenager gathered first outside a house of worship in Istanbul where his body lay.
His coffin - draped in red and covered in flowers - was then carried through the streets to the leafy hill-top cemetery, surrounded by huge crowds.
As his coffin was lowered into the ground, Berkin Elvan's distraught mother, Gulsum Elvan, cried out: "What am I to do now? They've taken my everything."
Mourners shouted "Berkin's murderers are the AKP police", referring to Mr Erdogan's ruling Justice and Development Party (AKP).
"The rage of mothers will suffocate the killers," screamed others.
Later, protesters in Istanbul threw fireworks into police lines while hundreds of people - including bystanders caught up in the melee, sheltered in a shopping centre and a hotel lobby as police fired tear gas and pepper spray.
The boy's father, Sami Elvan, told the BBC's Newshour programme that his son had become a "child of the people".
Asked how he would like him to be remembered, he said: "I want him to be known as a child killed by the state. He was just an innocent boy killed when he went out to buy bread."
Correspondents say Berkin Elvan became a symbol of the heavy-handed tactics used by police to rein in the biggest demonstrations against the prime minister.
His death brought the toll from last year's unrest to at least eight, including one policeman.
His mother had challenged Mr Erdogan, who praised police "heroism" during the protests.
"It's not God who took my son away but prime minister Erdogan," Mrs Elvan told reporters on Tuesday.
The renewed unrest is likely to add to pressure on Mr Erdogan, whose government has been rocked by an escalating corruption scandal ahead of elections that could decide his fate.
"How many young people have to die for Erdogan to resign? My only wish is for this fascism to end without spilling more blood," said retired worker Atilla Izmirlioglu.
Mr Erdogan has vowed to step down if the AKP, in power since 2002, loses in the local elections. The polls are seen as a key test of his popularity after last year's unrest and recent corruption scandals.
The sons of three former cabinet ministers were arrested and accused of corruption in December last year, while an audio recording surfaced that appeared to have caught Mr Erdogan talking to his son, Bilal, about hiding millions of euros in cash.
He said last month that the recording, allegedly tapped and then posted on social media, was fabricated and part of a "treacherous attack" by US-based Islamic cleric Fethullah Gulen.