Opposition tribesmen in Yemen say government snipers in the capital, Sana'a, have killed three supporters of tribal leader Sheikh Sadiq al-Ahmar.
The shootings Monday came a day after Vice President Abd al-Rab Mansur Hadi ordered his forces to vacate opposition-controlled areas of the capital, while al-Ahmar began to evacuate his militia from government buildings and called for an end to the fighting.
Scores of people have been killed in two weeks of clashes in Sana'a.
President Ali Abdullah Saleh handed power to Mr. Hadi before departing to Saudi Arabia, where the president is recovering from an operation to remove shrapnel from his chest.
Mr. Saleh was wounded in a rocket attack Friday on his presidential compound, and is expected to remain in Saudi Arabia for two weeks. Ruling party officials insist Mr. Saleh will return to Yemen, but analysts say it is not clear whether his Saudi hosts will allow him to go back home as president.
Mr. Hadi met with U.S. ambassador Gerald Feierstein Sunday to discuss cooperation with Yemen's opposition coalition. Mr. Hadi also met separately with military commanders, including several of Mr. Saleh's sons.
The Washington Post reported that U.S. and European diplomats, including Feierstein, urged Yemen's opposition to refrain from setting up interim government committees before Mr. Saleh is formally out of power. The newspaper cited a U.S. embassy spokeswoman as saying Washington is continuing attempts to push its onetime ally out of power.
Joyful celebrations broke out in Yemen Sunday, after word spread that the embattled Mr. Saleh had left the country. But expressions of concern also emerged about whether Mr. Saleh's 33 years in power have really come to an end.
Nearly 400 people have been killed since the popular uprising against Mr. Saleh began in January.