|Police was separating government supporters from anti-government protesters at Sanaa university [EPA]
Police shot and killed two protesters in Yemen's main southern city of Aden, medics said, while unrest in the capital Sanaa against the rule of Ali Abdullah Saleh, the president, continued for a sixth straight day.
Mohammed Ali Alwani, 21, was shot dead after clashes broke out between police and demonstrators, his father said. The other victim has not yet been identified.
Police in Aden fired shots into the air to try to break up around 500 protesters. Medics said one of the victims had been hit in the back.
The demonstrators hurled stones at police, set tyres and vehicles on fire and stormed a municipal building where heavy gunfire was heard.
Security forces, heavily deployed in Aden, arrested at least four people as they fired warning shots and tear gas to disperse protesters who had gathered at the Al-Ruweishat bus station in the Al-Mansura neighbourhood of Aden.
Protesters chanted "The people want to overthrow the regime" and "It's time to leave, Ali".
Later in the evening, people were demonstrating in Crater district.
In the capital Sanaa, at least 10 protesters were hurt amid clashes between students demanding the ouster of President Saleh and supporters of his ruling General People's Congress.
Hundreds of students had set off for Al-Sabiine square near the presidential palace, only to be attacked by a like number of Saleh loyalists armed with batons, stones and daggers.
The protesters responded by hurling stones, and when the violence spread into the campus of Sanaa university, where the march began, police fired warning shots.
"The thugs and supporters of the ruling party ... want to massacre" the students, the head of the university's student union, Radwan Masud, said, adding that 10 students had been hurt.
He vowed that the students would "continue their revolt and will not be hindered by the ruling party's actions."
Elsewhere in Sanaa, a sit-in by judges demanding greater independence for the judiciary and the sacking of the entire Supreme Judicial Council, including the justice minister, went into its second day outside the justice ministry.
The judges, who have poured into Sanaa from all over Yemen, also want higher salaries.
In other protests, workers in Sanaa gathered at several state-owned companies to demand that their managers to step down. They too also called for higher wages.
On Tuesday, police in Sanaa stepped in when supporters and opponents of the president clashed, leaving three injured. In Taez, south of the capital, the two sides also clashed.
On Monday, rocks and batons flew in the capital as protesters - mainly students and lawyers - confronted police and Saleh's supporters. Police also clashed with around 2,000 protesters in Sanaa on Sunday.
In the face of the unrest, Saleh has postponed a visit to the United States that had been planned for later this month, after the opposition agreed on Sunday to resume talks suspended since October.
Eyeing protests that brought down the presidents of Tunisiaand Egypt, Saleh, in power since 1978, pledged earlier this month not to stand in the next presidential elections. He also vowed not to pass on the reins of power to his son.
Of the 23 million people in Yemen, 40 per cent live on less than $2 a day and a third suffer chronic hunger.