SANAA, (Reuters) – Yemen launched air strikes on Shi’ite Muslim rebel hideouts on Saturday as fighting raged in the northern Saada province, military sources said, a day after the country’s president renewed a ceasefire offer.

“Heavy air strikes were directed on Saturday against Houthi strongholds, inflicting great losses as well as destroying a number of houses in which these elements were hiding,” a military source said.

The raids were mounted after the government reiterated its ceasefire conditions to the Houthi rebels, who rejected the proposal last week.

President Ali Abdullah Saleh said that the government “would face this sedition in a decisive way” if rebels rejected peace. “The armed forces are continuing to tighten their grip on the subversive elements in a number of areas,” another official source was quoted as saying in the ministry of defence’s online newspaper.

A local official in Saada told Reuters a group of Houthis had attacked a local clinic in a failed bid to kidnap a medical worker and plunder medical aid. They then attacked civilian houses before escaping, the official said.

Yemeni forces have used air strikes, tanks and artillery in the offensive described by officials as a determined attempt to crush the revolt, led by Abdul-Malik al-Houthi.

The U.S. embassy urged both parties to return to a ceasefire agreement reached last year and demanded both parties ensure the security of local and international relief workers in the region and the safe passage of emergency supplies to refuge camps.

The rebels, adherents of the Zaydi branch of Shi’ite Islam — a strongly tribal minority in mostly Sunni Muslim Yemen — oppose Yemen’s close ties with the United States and say they are defending their villages against government oppression.