Many protesters are angry at widespread corruption in a country where 40 per cent live on $2 a day or less [Reuters]

Anti-government unrest continued in Yemen on Tuesday with three people reported dead in a prison riot in support of protests and dozens reported injured when police opened fire on crowds in Sanaa, the Yemeni capital.

Policemen and security agents in civilian clothes opened fire as they tried to prevent people from joining thousands of protesters camped out in front of Sanaa University, witnesses told the Reuters news agency. Three of the injured were said to be in a serious condition.

Meanwhile, three prisoners at a Sanaa prison were reported killed and four others injured, Sharif Mobley, an inmate, told Al Jazeera via phone from within the prison.

Officials said at least one inmate was dead and dozens more injured as a consequence of the unrest which began on Monday when around 2,000 prisoners staged, taking a dozen guards hostage.

The inmates set their blankets and mattresses on fire before occupying the prison's main courtyard, an official who declined to be named because he is not authorised to speak to the media said.

The guards fired tear gas and gunshots into the air but failed to subdue the prisoners, the official added.

"At the moment there is no violence, there is no fighting," Mobley said on Tuesday morning, "but the situation is really looking very bad".

"The offices of the prison official have been burned down and the guards have all left and are now outside," he said.

"Authorities are outside the prison gates and we are inside the prison. We don't want to make any problems and are afraid for our lives."

Al Jazeera's Hashem Ahelbarra, reporting from Sanaa, said the "situation has not yet been contained".

"We have been told by different sources and inmates that the situation is really delicate ... inside the jail. It is has [also] become very tense in the capital," said our correspondent.

Yemen has been rocked by protests inspired by recent uprisings in Egypt and Tunisia that ousted those nations' leaders.

Many protesters are angry at widespread corruption in a country where 40 per cent live on $2 a day or less and where university graduates without connections struggle to get jobs. Youth unemployment is rampant.

Yemen is also riven with regional strife, with Shia rebels in the north and separatists in the south demanding fairer political participation.

A crowd of women joined a demonstration on Tuesday in the southern port city of Aden after a young protester was critically wounded by a bullet to the head during a rally there the previous day.

Also, tens of thousands took to the streets in the cities of the southern Ibb province on Tuesday, calling on the government to bring to justice those responsible for a deadly attack there on Sunday by what opposition activists said were "government thugs".

The opposition said the thugs descended on protesters camped out on a main square, killing one person and injuring scores.

For the first time since protests started in mid-February, graffiti against Saleh surfaced in his birthplace, the farming village of Sanhan just outside Sanaa.

Police said they were investigating who was behind the slogans painted on the village walls reading: "The people want the regime to step down."

Source: Al Jazeera and agencies