Yemen's government and forces loyal to a dissident general declared a cease-fire Tuesday, but residents in the capital said they later heard explosions and gunfire.

Officials from both sides confirmed the agreement started at 3:00 p.m. local time, however, people in Sana'a's Hasaba district heard fighting after that. Several previous truce accords have failed to hold.

The cease-fire accord came after at least six people were killed during fighting in the capital and Yemen's second-largest city, Taiz.

Medical workers reported two killed and at least 40 wounded in Sana'a when security forces fired on protesters who were calling for President Ali Abdullah Saleh to step down. Government troops also clashed with dissident soldiers.

Meanwhile, at least four civilians were killed in the southern city of Taiz in crossfire between protest-supporting tribesmen and government troops.

The U.S. State Department says the Yemeni president told the U.S. ambassador in Sana'a Tuesday that he is committed to a Gulf Cooperation Council plan that would have him step down amid political violence.

This echoed Mr. Saleh's statement Monday, welcoming a U.N. Security Council resolution urging him to sign the deal to leave office. The president said he is ready for talks to put a deal in motion.

A Gulf Cooperation Council proposal offers Mr. Saleh immunity from prosecution if he hands power to a deputy within 30 days. On at least three occasions, Mr. Saleh has refused to sign the plan, saying he first wants international guarantees about a timetable for its implementation.

Also Tuesday, Yemeni security officials say a military plane crashed while landing at an air base in the country's south, killing at least four of the 15 people on board.

Officials said the crash in Lahej province was likely caused by a technical problem.

Reports say the plane carried eight Syrians and seven Yemenis.