The university has been a focal point for protesters seeking to end the 32-year rule of autocratic President Ali Abdullah Saleh, a key US ally in the fight against Al-Qaeda's offshoot in the Arabian Peninsula.
Around 30 people have been killed in bloody protests across the impoverished and deeply tribal country, which was already battling a Shiite insurgency in the north, jihadists linked to Al-Qaeda, and a southern secessionist movement.
Interior Minister Motahar Rashad al-Masri denied anyone had been killed, but confirmed several people had been shot and one was in critical condition in hospital.
"Three injured protesters and three members of the security forces, some of whom were shot by bullets, are still at the hospital. No one was killed but one bystander, not a protester, was seriously wounded," he told AFP.
The medical official said three demonstrators were also wounded by gunfire, while some 60 others suffered light injuries from being beaten by police or inhaling tear gas.
A security official said 12 policemen were injured by rocks hurled by demonstrators.
Clashes erupted when police intervened to prevent students from expanding their tent city to a street close to University Square, where demonstrators have been camping since February 21.
A policeman who was injured in the violence said the protesters "opened fire" on the security forces, who responded in kind.
"When the protesters heard the shooting, around 1,000 of them gathered to attack security forces, but the police had to use tear gas to disperse them," he said.
Parliamentary opposition groups known as the Common Forum condemned the police.
"Even the medical teams coming to rescue the wounded were not spared the attacks," spokesman Mohammed Qahtan said in a statement.
The alliance said it held "Saleh personally accountable for the crime committed by the central security and the republican guard against the students."
Human rights group Amnesty International said the deadly raids on the protesters must stop.
"This is the second time in three weeks that protesters have been killed in late night raids by the security forces in the capital," said the London-based watchdog's deputy director for the Middle East and North Africa, Philip Luther.
"These disturbing heavy-handed tactics used with lethal effect against protesters must stop immediately. People must be allowed to assemble and protest in peace."
The United States called for an inquiry.
"We urge the government of Yemen to investigate and hold accountable those who appear to have utilized excessive force," State Department spokesman Mark Toner told reporters.
In other violence, a Saleh supporter was killed in clashes with anti-regime demonstrators in Seiyun in Hadramawt province in the southeast, a security official said.
In a separate incident, two people were wounded when police used batons and tear gas to disperse thousands of protesters who took to the streets of the town calling for Saleh's departure, witnesses and medical sources said.
Thousands also protested against the regime in the provincial capital Mukalla, witnesses said.
The opposition vowed on Sunday to step up protests after Saleh refused an ultimatum to resign by the end of the year. Instead the veteran leader vowed to serve out his current mandate until 2013.
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Around 30 people have been killed in bloody protests across the impoverished and deeply tribal country, which was already battling a Shiite insurgency in the north, jihadists linked to Al-Qaeda, and a southern secessionist movement.
Interior Minister Motahar Rashad al-Masri denied anyone had been killed, but confirmed several people had been shot and one was in critical condition in hospital.
"Three injured protesters and three members of the security forces, some of whom were shot by bullets, are still at the hospital. No one was killed but one bystander, not a protester, was seriously wounded," he told AFP.
The medical official said three demonstrators were also wounded by gunfire, while some 60 others suffered light injuries from being beaten by police or inhaling tear gas.
A security official said 12 policemen were injured by rocks hurled by demonstrators.
Clashes erupted when police intervened to prevent students from expanding their tent city to a street close to University Square, where demonstrators have been camping since February 21.
A policeman who was injured in the violence said the protesters "opened fire" on the security forces, who responded in kind.
"When the protesters heard the shooting, around 1,000 of them gathered to attack security forces, but the police had to use tear gas to disperse them," he said.
Parliamentary opposition groups known as the Common Forum condemned the police.
"Even the medical teams coming to rescue the wounded were not spared the attacks," spokesman Mohammed Qahtan said in a statement.
The alliance said it held "Saleh personally accountable for the crime committed by the central security and the republican guard against the students."
Human rights group Amnesty International said the deadly raids on the protesters must stop.
"This is the second time in three weeks that protesters have been killed in late night raids by the security forces in the capital," said the London-based watchdog's deputy director for the Middle East and North Africa, Philip Luther.
"These disturbing heavy-handed tactics used with lethal effect against protesters must stop immediately. People must be allowed to assemble and protest in peace."
The United States called for an inquiry.
"We urge the government of Yemen to investigate and hold accountable those who appear to have utilized excessive force," State Department spokesman Mark Toner told reporters.
In other violence, a Saleh supporter was killed in clashes with anti-regime demonstrators in Seiyun in Hadramawt province in the southeast, a security official said.
In a separate incident, two people were wounded when police used batons and tear gas to disperse thousands of protesters who took to the streets of the town calling for Saleh's departure, witnesses and medical sources said.
Thousands also protested against the regime in the provincial capital Mukalla, witnesses said.
The opposition vowed on Sunday to step up protests after Saleh refused an ultimatum to resign by the end of the year. Instead the veteran leader vowed to serve out his current mandate until 2013.
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