SANAA/RIYADH - Yemeni Shi'ite rebels denied on Saturday carrying out an assassination attempt on an Interior Ministry official which was staged only hours after a ceasefire agreement came into force. Yemen's government and rebel leader Abdul Malik al-Houthi agreed late on Thursday that a truce would begin at midnight, aiming to halt one of the country's three conflicts. Interior Ministry undersecretary Mohammed al-Qawsi, whose car was shot at on Friday in the northern city of Saada, said shortly after the attack that minor violations had occurred because not everyone was aware of the ceasefire, but that the deal still held. The rebels issued the denial on their website, and said Houthi had asked his supporters to clear mines and open roads. Some of the 250,000 people displaced by the war were returning to their homes, they added. Roads to Saada, centre of the mountainous province where many of the rebels are based, were now clear, and the truce was being respected by the insurgents, the rebel statement said. Yemen's government, which is also battling al Qaeda and a separatist movement in the south, had been exchanging ceasefire proposals with the Shi'ite rebels for several days. Yemeni forces have been fighting Houthi's supporters since 2004 and previous ceasefires have not lasted. Turmoil in Yemen has raised fears that the country may become a failed state, allowing al-Qaeda to use it as a base for attacks in the region and beyond. The Nigerian accused of trying to blow up a US plane in December had links to Yemen.' Top oil exporter Saudi Arabia gave the rebels on Saturday 48 hours to hand over five Saudi soldiers they have captured. "There are five prisoners who must be returned and they were given a 48-hour time limit," said Assistant Minister of Defence Prince Khaled bin Sultan, quoted by state news agency SPA.