Yemeni President Ali Abdullah Saleh on Tuesday used fighter jets to strike at tribesmen who attacked government forces, the Associated Press reports.

Just a week after Saleh's eleventh hour face-heel turn in which he refused to sign the much hailed transition agreement brokered by the Gulf Cooperative Council that would see him leave office, Yemen's president has dug in and bullets are flying again.

Hamid Assem, a Yemeni tribal official, told the AP news agency that fighter jets pounded mountain villages outside the capital after anti-government tribesmen ambushed troops loyal to the embattled Saleh.

The warplanes hit the villages of Khaliqa and Massoura, located some 40 kilometres north of Sana'a, on Tuesday, according to Assem. He told the AP four tribesmen were killed and six mud brick houses were destroyed.

Assem says the airstrikes took place after members of the anti-government Mehem tribe attacked troops loyal to President Ali Abdullah Saleh.

The attack comes a day after Monday's brutal crackdown on protesters in the southern city of Tiaz.

Witnesses and medics further told AP that Yemeni security forces Monday used live-fire on protesters in a bid to break up a day-old sit-in, killing a shopkeeper and three protesters, and wounding 80.

The crackdown came a day after demonstrators, joined by striking teachers, took over a main street in the city of Taiz and set up tents.

Saleh's government says the protesters were obstructing traffic and blocking access to government offices.

Yemenis have been staging daily protests for three months calling for Saleh's ouster.