New fighting flared in Yemen's capital city, Sanaa, on Tuesday between tribesmen loyal to President Ali Abdullah Saleh and soldiers backing anti-government protesters.
A day after as many as 17 people died in the southern city of Taiz, at least three people were reportedly killed in Sanaa when pro-Saleh tribesmen attacked a barracks housing troops that had switched sides to back the opposition.
The anti-Saleh camp has reportedly said that an approach by tribal chiefs sent by the government to mediate with the soldiers was in fact an attempt to assassinate Gen. Ali Mohsen, a key general who turned against Saleh last month.
"The issue appeared to be a trick to assassinate Ali Mohsen, intermediaries and a group of tribal sheikhs," a statement from Mohsen's office said, Reuters reported.
Saleh's defense ministry, however, said that three people died when the tribesmen were attacked by protesters and Mohsen's troops, who are protecting the activists.
Meanwhile, plainclothes security men also reportedly opened fire on anti-government protesters in Taiz on Tuesday.
More than 100 people have been killed since protests against Saleh began in February, soon after the downfall of Hosni Mubarak in Egypt.
Protesters are calling for Saleh to step aside after 32 years in power, but he has signaled that he has no plans to leave immediately, according to the BBC.
The U.S. has reportedly dropped its support for Saleh, a longtime ally in the fight against Al Qaeda in the region to whom it has provided millions of dollars in counterterrorism aid in the hopes of thwarting attacks on American soil.
The U.S. State Department has called the violence in Yemen "appalling."
Adding to the international pressure against Saleh, with the EU's foreign policy chief, Catherine Ashton, issued a statement Tuesday that said "the transition must begin now."
The office of the U.N. High Commissioner for Human Rights expressed alarm over Monday's shootings, referring to "reports of disproportionate and excessive use of force, including machine guns, against peaceful protesters in Taiz."
Meanwhile, according to the Financial Times, Gulf Co-operation Council embassies in Sanaa has offered to host talks between both sides.
Saleh's government has said it will accept an invitation to attend talks in Riyadh. But Aidroos al Naqeeb, a senior official with one of the larger opposition parties, said that opposition groups did not want "a discussion that doesn’t deal with the immediate transfer of power."