At least seven people were killed, including four policemen who clashed with a dissident army unit, security sources and medics said, as anti-regime protesters rallied across Yemen on Wednesday.
"Police attacked an army checkpoint in Jawlat Amran" in north Sanaa, "killing one officer and wounding two soldiers," a military official told AFP.
The four policemen died as the rival security forces traded fire with automatic weapons and rocket-propelled grenades late on Tuesday, he said.
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The targeted army unit operates under northwestern military commander, General Ali Mohsen al-Ahmar, who has sided with the protesters and accused regime supporters of trying to assassinate him, the official said.
However, the interior ministry later accused the army unit of having sparked the fighting by attacking police.
"Several policemen were injured in the clash," the ministry said in a statement, without giving other details or mentioning casualties on the army's side.
Opening fire
In the south of the country, soldiers shot dead two anti-government protesters and wounded nine others in different sectors of the port city of Aden, medics and witnesses said.
They said the army opened fire as protesters tried to set up roadblocks to enforce a partial general strike, which demonstrators have vowed to stage in Aden every Saturday and Wednesday until President Ali Abdullah Saleh's fall.
They were the first deaths for a month in the city, the scene of deadly protests between late February and early March.
Aden's security chief General Ghazi Ahmed Ali said: "Armed groups from the Common Forum (an alliance of parliamentary groups) and the (secessionist) Southern Movement blocked the roads and tried to break into police stations."
Five civilians and four policemen were wounded in an attack on a station in the district of Al-Mansura, he said.
Protests swept provinces across the country on Wednesday in response to calls by the Youth for Change, a coalition of groups that has led anti-Saleh demonstrations since late January.
The largest rally was held in the flashpoint city of Taez, south of Sanaa, where more than 20 people were killed in clashes with security forces earlier this month.
Saleh loyalists also took to the streets, but in smaller numbers, in several provinces and chanted their support for the embattled leader.
Yemen's oil-rich Arab neighbours in the Gulf have urged Saleh, in power since 1978, to ensure a peaceful transition of power to Vice President Abdrabuh Mansur Hadi and a national unity government led by the opposition.
But protesters have rejected the proposal, demanding that Saleh's entire regime be dismantled and he be prosecuted.
Saleh, for his part, has accepted in principle the initiative of the six-nation Gulf Cooperation Council but without spelling out clearly whether or when he would step down.
He has so far insisted on overseeing any transition, fearful of being dumped out of office and faced with prosecution like his ally, Egypt's president Hosni Mubarak, who was ousted on February 11 following mass demonstrations.
Opposition groups in parliament have remained reserved, apparently fearful of the reaction of protesters on the streets whose ranks have suffered more than 125 deaths in clashes with Saleh's security forces.
