More than 100 people were injured in Bangladesh on Saturday after police fired rubber bullets at student protesters, a doctor and witnesses said.
The violence was a major escalation in the stand-off between the government and young demonstrators since students and pupils brought parts of the capital Dhaka to a standstill last week with demonstrations against poor road safety after two teenagers were killed by a speeding bus.
Bangladesh's transport sector is widely regarded as corrupt, unregulated and dangerous, and as news of the teenagers' deaths spread rapidly on social media they became a catalyst for an outpouring of anger against the government.
On Saturday the protests turned violent in Dhaka's Jigatala neighbourhood.
Witnesses said police fired rubber bullets and teargas at demonstrators and that alleged pro-government activists attacked youngsters, including some of those rushing to nearby hospitals for treatment.
Police denied they fired rubber bullets or teargas at the protesters.
"It's not true. Nothing happened at Jigatala," Dhaka police spokesman Masudur Rahman told AFP.
However, hospital staff said dozens of people had been injured, some seriously.
"We have treated more than 115 injured students so far since the afternoon," emergency ward doctor Abdus Shabbir said. Some of the badly hurt had injuries consistent with rubber bullets, he said.
"A few of them were in very bad condition."
A protester said students were holding protests peacefully on the road when they were attacked.
"We all are feeling threatened here. We wanted a peaceful protest. We don't want any trouble occurring around here. Yet rubber bullets were shot at our brothers," Sabbir Hossain, a student, said.
Road transport minister Obaidul Quader rejected allegations that party cadres from the ruling Awami League party had attacked the students.
He said the party office, which is close to Jigatala, was vandalised by unidentified youths in school uniforms moments before the clashes erupted.
Students and unidentified young men fought with sticks and rocks, leaving several wounded, said an AFP photographer at the scene of one of the clashes.
The government of Prime Minister Sheikh Hasina has ruled Bangladesh since 2009 but in recent months it has been shaken by mass protests demanding an end to the decades-old system of discriminatory civil service recruitment.
Several powerful ministers have pleaded with students to return to their classes, amid worries the unprecedented teenage anger could turn into widespread anti-government protests before general elections later this year.
But their pleas have had little effect.
Earlier on Saturday thousands of pupils wearing school uniforms defied rain to block major intersections in the capital for the seventh consecutive day.
Teenagers as young as 13 were seen on Dhaka's notoriously clogged roads checking whether cars and buses had valid licences and were in a roadworthy condition.
"We won't leave the roads until our demands are met. We want safe roads and safe drivers," said protester Al Miran.
An insensitive comment by Shajahan Khan, a government minister with ties to powerful transport unions, added to the anger on the streets earlier in the week.
Mr Khan questioned why there was such an uproar over the two Dhaka children but no reaction when 33 people were killed in an Indian bus crash the day before.
There have been widespread social media demands for the minister's resignation despite his subsequent apology.
The education ministry shut down high schools on Thursday in an effort to quell unrest, promising pupils their demands for road safety reforms would be considered.
Dhaka suffers from daily gridlock but congestion has been exacerbated by blockades set up across the city since Sunday.
The embassies of the US and Australia warned of significant delays and disruptions as a result of the protests across Dhaka and elsewhere in the country.