SANAA -Yemeni troops clashed with insurgents, killing 20, and the government said on Sunday it had rejected the latest ceasefire offer by northern rebels. Rebel snipers also fought with Saudi soldiers, despite a Saudi declaration last week it had defeated the rebels. Yemen has been fighting the rebels, who complain of marginalization, on and off since 2004, but the conflict intensified last summer and then again in November when it drew in neighboring Saudi Arabia, the world's top oil exporter. Yemeni soldiers clashed with rebels in the northern provinces of Malahidh and Saada, killing 20, including a leader responsible for training, state media reported on Sunday. The government said it had rejected a new ceasefire offer. Rebel leader Abdul-Malik al-Houthi said on Saturday he was prepared to accept government conditions for a truce, days after he made a ceasefire offer to Saudi Arabia and said they had withdrawn from Saudi territory. "The Houthi offer is rejected as it does not vow to end attacks on Saudi Arabia and because it sets as a condition an end to military operations first (by the government)," a government official told Reuters. The rebels said they would accept five conditions set by Sanaa for a ceasefire that include the removal of rebel checkpoints, withdrawal of forces and clarification of the fate of kidnapped foreigners. The rebels also must return captured military and civilian equipment and not enter local politics.