Troops have again fired on protesters in Yemen's capital, Sanaa, as clashes continue between President Ali Abdullah Saleh's supporters and armed tribesmen.
Shells have hit the presidential compound in the Yemeni capital, Sanaa, as pitched battles continue between government forces and armed tribesmen.
Gun and artillery fire were reported near a university campus where demonstrators demanding Mr Saleh's resignation have been holding a sit-in.
One report quoted the governing party as saying the prime minister and speaker of parliament were wounded.
Rallies both in support of and against Mr Saleh are expected later.
Earlier, troops shelled the home in the south of Sanaa of Sheikh Hamid al-Ahmar, a brother of the tribal leader whose supporters they are fighting.
Overnight, tribesmen siding with the opposition fought pitched battles with troops in northern areas of the city.
Thousands meanwhile attended a funeral for 50 people killed in the violence.
The United States has sent an envoy to the Gulf to discuss ways of stopping the violence, which has brought Yemen to the brink of civil war.
The United States has sent an envoy to the Gulf to discuss ways of stopping the violence, which has brought Yemen to the brink of civil war.
More than 350 people have been killed since the uprising started in January, but least 135 of them have died in the past 10 days.
More than 350 people have been killed since the uprising started in January, but least 135 of them have died in the past 10 days.
Western and regional powers have been urging President Saleh to sign a Gulf Co-operation Council-brokered deal that would see him hand over to his deputy in return for an amnesty from prosecution.
Western and regional powers have been urging President Saleh to sign a Gulf Co-operation Council-brokered deal that would see him hand over to his deputy in return for an amnesty from prosecution.
He has agreed to sign on several occasions, but then backed out.
He has agreed to sign on several occasions, but then backed out.
Funeral procession
The BBC's Lina Sinjab in Sanaa says anti-government protesters are preparing to take to the capital's streets again after Friday prayers, as they have done every week during the past four months.
But this time opposition activists are particularly concerned that they may be attacked by security forces and Mr Saleh's supporters, as protesters were in the southern city of Taiz earlier this week, our correspondent adds.
At least 50 people have been killed in Taiz since Sunday, according to the UN.
On Monday, troops used force to clear a square that had been occupied for months by protesters, and have fired on people attempting to return there.
Warning shots were fired at protesters as they gathered at a mosque in Taiz for midday prayers on Friday.
Troops also fired machine-guns and artillery at protesters and breakaway army units protecting them in central Sanaa on Friday morning.
Three shells exploded near the campus of Sanaa University, the centre of the demonstrations against Mr Saleh, and near troops loyal to dissident Gen Ali Mohsen al-Ahmar, witnesses told the AFP news agency.
Medics told the Reuters news agency that seven people had been hurt.
The violence came as a mass funeral was held for some 50 opposition members killed in fighting this week, activists told Reuters.
Video footage showed coffins being carried through the capital's streets in a procession attended by tens of thousands of people.
Tribesman advance
Explosions were also heard from the Hassaba district of northern Sanaa, where government forces have been fighting tribesmen loyal to Sheikh Sadiq al-Ahmar, head of the Hashid tribal confederation.
Witnesses said Sheikh Ahmar's home in the Hassaba district was being shelled.
There were also fierce clashes overnight, with artillery and rockets hitting buildings in and around Sheikh Ahmar's compound.
Troops set fire to the headquarters of Suhail TV, a private station owned by one of Sheikh Ahmar's nine brothers.
State TV showed pictures of the burning offices of national airline Yemenia, blaming it on the tribesmen.
The defence ministry said special forces personnel led by Mr Saleh's son, Ahmed, had been deployed for the first time.
It said they would help "liberate" more than a dozen ministries and other government buildings occupied by the tribesmen since fighting began last week.
A truce agreed on Friday collapsed after four days, with each side blaming the other.
Tribal sources meanwhile said several thousand tribesmen were heading to the capital from surrounding areas to join the fighting.
"We won't leave Ahmar alone and will enter Sanaa to stand with him and fight alongside him," one tribal leader told the Associated Press.
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