At least 11 people were killed in heavy fighting in the Yemeni city of Taiz on Friday, a day after a UN envoy began a new mission to push President Ali Abdullah Saleh to quit under a Gulf peace plan.
Witnesses and medical staff said at least 25 people were also wounded in the fighting between Saleh's Republican Guards and opposition tribesmen in Yemen's third largest city, a hotbed of anti-Saleh protests some 200 km south of Sanaa.
Witnesses said two children and three woman were among those killed in tank and mortar fire aimed at the al-Rawda and Zaid al-Moshki districts as well as Freedom Square, where demonstrators demanding an end to Saleh's 33-year-long rule gather for Muslim noon prayers every Friday.
In Sanaa, tens of thousands of anti-Saleh protesters attended prayers on a main road. Some demanded the president be tried for what they called his crimes against the Yemeni people.
Separate prayers were held by thousands of Saleh supporters in the capital. There were no reports of violence in Sanaa.
The fighting in Taiz started on Thursday after gunmen shot and critically wounded a soldier stationed at a government building. This was followed by the killing of a pro-Saleh tribal leader and the wounding of one of his bodyguards.
UN envoy Jamal Benomar arrived in Sanaa on Thursday to encourage "an inclusive transition process that meets the needs and aspirations of all Yemenis," a spokesman said.
Martin Nesirky, spokesman for UN Secretary-General Ban Ki-moon, said Benomar would report back to Ban, who is to inform the UN Security Council about the implementation of a resolution adopted last month that called on Saleh to accept a Gulf-brokered plan under which he would step down.
Saleh, who has clung to office despite pressure at home and abroad, has repeatedly wriggled out of signing the deal.
France has said the European Union will discuss freezing Saleh's assets to increase the pressure for his departure.
The plan calls for Saleh to hand power to his deputy, Abd-Rabbu Mansour Hadi, who will oversee the formation of a national unity government ahead of an early presidential election.
Benomar met Foreign Minister Abubakr al-Qirbi in Sanaa on Thursday and was expected to meet Hadi, as well as opposition leaders who are due to return from a Gulf tour within days.
Saudi Arabia, the world's largest oil exporter which shares a long and porous border with Yemen, has been worried that violence in Yemen may strengthen al-Qaeda militants based there who have launched attacks in the past on US and Saudi targets.
