Yemen's opposition on Sunday accused outgoing President Ali Abdullah Saleh of trying to torpedo a power transfer deal by sparking a new crisis, as troops loyal to him clashed with opposition forces, killing three.
The violence was evidence that the president's signature on a power transfer deal has not ended months of turmoil that have benefited al-Qaida-linked militants.
Sunday's clashes followed Saleh's decision not to leave the country, a move likely to embolden his relatives, who control key security posts.
His opponents demand the removal of all of Saleh's relatives from top security positions. Huge crowds of protesters have called for Saleh himself to be put on trial for the killing of hundreds of protesters, though the power transfer deal gives him immunity from prosecution.
Vice President Abed Rabbo Mansour Hadi told his new national unity government on Sunday, in their first official session, that the power transfer agreement, engineered by Yemen's powerful Gulf Arab neighbors, must be implemented soon.
"We need to move vigorously and effectively to implement the Gulf initiative and its mechanisms," he said.
The new government's first task is to push through the law shielding Saleh from prosecution for alleged corruption and for violence against protesters. Saleh made that a condition for signing the deal to relinquish power after 33 years of rule over the Arab world's poorest nation.
Yet more than a month after Saleh signed, and after the possibility of his flying to the U.S. was raised, Saleh is still in Yemen, still wielding significant power and showing few, if any, signs of giving in.
Ten months of mass protests and armed clashes between forces loyal to Saleh and his opponents, including army units that followed powerful tribal leaders siding with the opposition, have left a power vacuum. The Yemen branch of al-Qaida, considered one of the world's most dangerous, has taken advantage of that to dig in to positions in the country's south, taking over towns and villages.
Yemen's military fights frequent battles with the Islamist militants but has failed to dislodge them.
In the latest skirmish between Saleh backers and opponents, anti-government tribesmen in el-Fardha Nehem region, about 50 miles (80 kilometers) northeast of the capital Sanaa, said two people were killed and two others wounded when Saleh's Republican Guards, led by his son, shelled their homes.
Opposition spokesman Mohamed Sabri accused Saleh of undercutting security as a way of arguing that he must stay in power.
"This man does not respect his commitments with others," Sabri said. "Saleh is creating a new crisis."
In the capital, a civilian bystander was killed when Republican Guard troops clashed with supporters of tribal chief Sadeq al-Ahmar, who was once a regime ally, but defected to the opposition in March, activists said.
Supporters of al-Ahmar and Saleh's troops exchanged fire in Sanaa's northern district of Hassaba, according to a security official and witnesses, resulting in the death of the bystander. The official spoke on condition of anonymity because he was not authorized to release the information.
The fighting Sunday ended after the vice president held talks with both sides. He was also able to quell violence in el-Fardha Nehem region.
Large crowds of Yemenis rallied in major cities Sunday, demanding the outgoing president be put on trial for the deaths of protesters.
The U.N. estimates that hundreds of protesters have been killed and thousands wounded since last February, when anti-government protests erupted across major cities.
Tens of thousands marched in the streets of Sanaa, chanting that Saleh "must stand before a judge." Another large crowd of marchers echoed the chant in Taiz, Yemen's second largest city.
Activist Fathi al-Hamadi said the "only place for Saleh to go to is the court dock."