SANAA – The leader of Yemen's Shi'ite rebels on Monday offered a ceasefire to Saudi Arabia and said his fighters would withdraw from the kingdom's territory to avoid more civilian casualties. The announcement by Abdul-Malik al-Houthi followed three months of border fighting between Shi'ite rebels and Saudi forces who also used their air force to bomb rebel targets. "To avoid more bloodshed and to stop aggression on civilians ... we offer this initiative," Houthi said in an audio recording posted on the Internet. He warned that if Saudi Arabia did not end its hostilities in return, the rebels would wage an "open war" on the world's top oil exporter. Yemen's central government has been fighting the rebels on and off since 2004, but the conflict intensified last summer when Sanaa launched Operation Scorched Earth to quash the latest upsurge in violence. Saudi Arabia stepped into the fray in November when rebels seized some Saudi territory, prompting Riyadh to wage a major military offensive against them. The conflict raging in the north has displaced around 200,000 people, according to the United Nations. The International Committee of the Red Cross (ICRC) said on Monday humanitarian conditions in northern Yemen were worse than ever and that fighting had dramatically worsened the fate of Yemeni civilians. Yemen is also in the throes of a crackdown on al-Qaeda whose regional wing is based in the country, while also trying to contain simmering unrest from a southern separatist movement. Western powers and Riyadh fear Yemen will become a failed state, allowing a resurgent al-Qaeda to exploit chaos to use the country as a base for more international attacks. Yemen's Interior Ministry said on its website that about 30 suspected al Qaeda militants were killed recently in a campaign against the group, but did not say when the deaths took place. Al-Qaeda killed three soldiers in the south of the country in a Sunday attack, a security official said on Monday.