More than 20 students were injured when police in Bangladesh's capital fired tear gas and used batons and rubber bullets to disperse hundreds of protesters demanding better road safety.
Young people angry over the traffic deaths of two fellow students had been demonstrating for days in Dhaka, culminating in violence in which they threw stones at police.
The city of 7 million remained largely cut off, as buses refused to enter the city from other parts of the country.
Witnesses and media reports said chaos broke out in as police and ruling party officials swooped in on the students.
The protests, which began earlier this week after two college students were struck and killed by a pair of buses, have paralysed Dhaka.
Students have stopped thousands of vehicles, including those of top officials and judges, demanding to see whether the cars were registered and the drivers licensed.
A top leader of the ruling Awami League said some "criminals" in school uniforms joined the violence. But many protesters blamed the student wing of the ruling party for the attacks.
The English-language Daily Star reported that up to 25 people were injured.
The protests are an embarrassment for the government of prime minister Sheikh Hasina ahead of a general election in December, and she has pledged to fulfil the students’ demands.
The students are demanding safer roads in Bangladesh, where corruption is rife, making it easy for unlicensed drivers and unregistered vehicles to use the roads.
At least 12,000 people die each year in road accidents often blamed on faulty vehicles, reckless driving and lax traffic enforcement.
Associated Press contributed to this report.
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