Yemen's government signed a cease-fire with a dissident general Tuesday to try to end weeks of worsening bloodshed but sporadic explosions and gunfire were still heard in the north of the capital.
After months of protests against President Ali Abdullah Saleh's 33-year rule, a standoff between him and an opposition made up of protesters, tribesmen and renegade soldiers tipped into street fighting last month. Previous truces collapsed.
A government official said the cease-fire deal between Saleh's administration and the breakaway general, Ali Mohsen, would take effect at 3 p.m. (1200 GMT) Tuesday but residents of the Hasaba and Sofan neighbourhoods in northern Sanaa said they heard explosions after that time.
State media later said the truce was stabilizing and a mediator expressed optimism it would hold.
In spite of the violations of the cease-fire, the mediation committee is still ... making contacts with all parties to implement the agreement. The issue is not easy but we are still optimistic, the mediator told Reuters.
Saleh, defying hostile demonstrations inspired by protests across the Arab world, has refused to step down in line with a plan brokered by Gulf states. The United States and Saudi Arabia fear the upheaval is giving al Qaeda's local wing more room to operate in Yemen, the poorest Arab country.
In Washington, the State Department said Saleh called in U.S. Ambassador Gerald Feierstein to tell him about the cease-fire and his intention to sign the Gulf Cooperation Council transition plan for Yemen.
State Department spokeswoman Victoria Nuland said the United States was encouraged by the developments.
We do consider it a good step, both that President Saleh is reaffirming his commitment to the GCC agreement and that he understands and is supportive of the fact that the violence has got to end so that we can set the conditions for discussions about Yemen's diplomatic future, Nuland told reporters.
Earlier Tuesday, security forces opened fire on a protest march in Sanaa, killing two people, witnesses said. An opposition source said a third person was killed in shelling by Saleh's troops in the Sofan district.
In fighting between state forces and opposition fighters in the city of Taiz Tuesday, eight civilians were killed and more than 30 wounded, an opposition source said. The government said three members of its security forces were killed there.
Under the cease-fire mediated by a local committee, both sides agreed to dismantle armed checkpoints across the capital and release all of the people kidnapped during months of anti-government protests.
The agreement came four days after a United Nations Security Council resolution condemned violence in Yemen and urged Saleh to sign the Gulf initiative to hand over power.
Saleh, who welcomed the Security Council resolution on Monday, has backed out of the Gulf initiative at the last minute three times and says he will transfer power only to safe hands.
A Yemeni military plane crash-landed at an air base in Lahej province in the south, killing nine passengers, eight Syrian engineers and one Yemeni engineer, doctors and army officials said.
A security official said a technical fault was probably to blame for the crash of the Russian-made Antonov plane and that the incident would be investigated.
Lahej borders Abyan province, where the Yemeni army is fighting to regain control of territory seized by suspected al Qaeda militants, who have benefited from political upheaval and weak government control over parts of the country.
Late Monday, an Uzbek doctor was abducted in the northern province and tribal stronghold of Maarib. A tribal source said he was kidnapped by tribesmen to put pressure on the government to release some jailed comrades.
(Reporting by Mohamed Sudam in Sanaa and Mohammed Mukhashaf in Aden; Writing by Isabel Coles; Editing by Tim Pearce and John O'Callaghan)