Yemen unrest: Saleh forces 'shell Sanaa protest camp'
Government forces in Yemen have continued firing shells at a protester camp in the capital, killing at least seven people, witnesses say.
Gun battles between government troops and their enemies have raged all day, moving into the wealthiest suburbs of the capital Sanaa.
Government soldiers launched a bloody assault on protesters two days ago in which dozens have now died.
The protesters want President Ali Abdullah Saleh to stand down.
Mr Saleh, who has ruled the country for more than three decades, has been in Saudi Arabia since June, when he was seriously injured in a rocket attack on his presidential compound.
He has refused to stand down and is promising to return to the country.
The latest violence is the worst the country has seen for several months.
Witnesses say government snipers have been shooting protesters from the rooftops in Sanaa, and the main protest camp in Change Square has come under intense shelling.
According to doctors, three opposition soldiers, three protesters and a civilian bystander were killed in rocket attacks on the protester camp on Tuesday.
Manea al-Matari, a protester, told Reuters news agency: "We were walking back from prayers. All of a sudden a rocket hit close by from out of nowhere, and some people fell down.
"And then a second one came and that's when we saw the two martyred."
Government forces have also been involved in full-scale combat with the army unit that defected to the protesters months ago.
Witnesses say military aircraft have been targeting positions held by the opposition troops.
However, ministers have consistently denied that their soldiers have targeted civilians or peaceful demonstrators, telling the BBC that the unrest was initiated by al-Qaeda-linked forces within the opposition.
The BBC's Middle East correspondent Jon Leyne says civilian protesters are increasingly caught in the middle of a conventional military battle between the Saleh loyalists and troops backing the protests.
On Monday, one report said opposition forces had seized a base of the republican guards - an elite force run by the president's son Ahmed.
Analysts say the final battle for control of the country could pit the republican guards against opposition troops and their tribal allies.
On Tuesday, fighting also broke out in the Hadda neighbourhood, which is home to government officials and several members of Mr Saleh's inner circle.
Reports say the gun battles there were likely to be between government troops and tribes who have long been hostile to the Saleh regime.
Mass protests and killings by security forces have also been reported in the cities of Taiz and Aden in recent days.
Envoys from the UN and the Gulf Cooperation Council arrived in Yemen on Monday in a bid to sort out a deal to end the bloodshed.
Yemen is the poorest country in the Arab world. It faces multiple crises and some analysts already see it as a failed state.
It has an active al-Qaeda cell, as well as a separatist movement in the south and a Shia-dominated uprising in the north.
Aid agencies warn that the country is suffering a severe humanitarian crisis with about 7.5 million Yemenis - one third of the population - going hungry.
Mr Saleh had enjoyed long periods of support from the US and West by casting himself as an implacable enemy of al-Qaeda and other extremists.