SAN'A, Yemen - Yemeni warplanes bombed a northern province bordering Saudi Arabia for a second straight day, the province's Shiite rebels and local officials said Thursday, in an ongoing offensive that has brought casualties and pushed the area close to an all-out war.

The government offensive in the northern Saada province started Tuesday, after rebels claimed they had wrested more control of the region from Sunni-led government troops. Authorities in turn promised to crush the Shiite rebel uprising "with an iron-fist."

Saada has been the scene of a five-year rebellion by a Shiite minority that has further destabilized this U.S.-allied country as it faces a resurgent threat from al Qaeda, a separate secessionist uprising in the south and an economic downturn from plunging oil prices.

The latest attacks came a day after air force planes hit an outdoor market in the provincial town of Haydan, killing several civilians, according to rebels and local officials.

The rebels and local officials claimed that in renewed bombardment, with sorties overnight and into early Thursday, military planes bombed several other Saada towns and rebel positions.

The officials said "dozens" of people were killed and wounded in the renewed bombardment, including in the towns of Sihar, Miran and Al-Maqash.

A rebel website said Wednesday's air government strike hit a marketplace in Hadyan as residents were doing their early morning shopping.

A statement by the rebel leader Abdel Malik al-Hawthi, posted on the group's Web site, described the attack as "a mass carnage" and appealed to Yemen's political parties to condemn the government strikes. It said an unspecified number of civilians died and posted gruesome photos of victims allegedly killed in the bombardment.

The reports could not be independently confirmed as the remote and lawless area is mostly off limits.

Reflecting the escalating conflict, the government imposed late Wednesday a state of emergency on the province, with a nightly curfew in Saada and other nearby towns.

A government committee also set several conditions on the rebels to halt the offensive, including leaving their positions, disarming and handing over soldiers and civilians captured in the fighting.

There were also conflicting numbers of casualties reported.

On Wednesday, a local government official said 20 rebels were killed. A local Health Ministry official said 12 others died in fighting across Saada and 51 were injured. Hundreds were reported to have fled the clashes.

The officials in Saada all spoke on condition of anonymity because they were not authorized to speak to the media.

Yemen, an impoverished Arabian peninsula country that is also the ancestral homeland of Osama bin Laden, has a weak central government that has little authority outside the major cities.

Its instability has been a key concern for both the U.S. and Saudi Arabia, where newspaper editorials have been warning of regional impact of the troubles in Yemen.

A commentary this week in Asharq Al-Awssat, a newspaper owned by the Saudi royal family, warned that "this disaster threatens Yemeni unity as a whole, as well as the security of Saudi Arabia and all Gulf Cooperation Council countries without exception."