Suspected Al-Qaeda rebels ambushed an army vehicle and killed five soldiers near the Yemeni town of Marib, east of the capital Sanaa, on Friday, a security official told AFP. \"The vehicle was ambushed with an RPG (rocket-propelled grenade) and all five soldiers inside died,\" the official said. \"Al-Qaeda is suspected of carrying out this attack.\" The Saudi and Yemeni Al-Qaeda branches merged in January 2009 to form the Yemen-based Al-Qaeda of the Arabian Peninsula (AQAP). Four days after US forces killed Al-Qaeda leader Osama bin Laden in a commando raid on his hideout in Pakistan, a US drone targeted US-Yemeni cleric and terror suspect Anwar al-Awlaqi who narrowly escaped in southern Yemen. Yemen has come under intense pressure to crack down on jihadists\' local franchise since a Christmas 2009 attempt to blow up a US airliner that was claimed by AQAP. Washington has expressed fears that Al-Qaeda could take advantage of a prolonged political crisis in Yemen, bin Laden\'s ancestral homeland, where President Ali Abdullah Saleh has faced mass protests since late January calling for him to step down. Saleh, who is clinging to power, has been a close US ally in Washington\'s fight against Al-Qaeda. Friday\'s ambush by the jihadists came a day after Yemeni forces killed 19 demonstrators opposed to Saleh over a 24-hour period prompting renewed international criticism of his government for using excessive force. Supporters and opponents of the veteran president, in power in Sanaa since 1978, were due to hold rival mass rallies in the capital after the main weekly Muslim prayers later on Friday. Opposition activists urged impoverished Yemen\'s wealthy Gulf Arab neighbours, who have been mediating in the crisis, to support their \"people\'s revolution.\" Gar-rich Qatar announced on Thursday that it was withdrawing from the six-nation Gulf Cooperation Council\'s mediation effort. Qatari Prime Minister Sheikh Hamad bin Jassem al-Thani informed GCC chief Abdullatif al-Zayani of his government\'s decision by telephone, a foreign ministry spokesman said late on Thursday. The decision was based on \"indecision and delays in the signature of the proposed agreement\" and \"the intensity of clashes\" in Yemen. The GCC chief earlier condemned the violence and called on all parties to sign up to the bloc\'s proposals for a peaceful transition. Saleh has so far refused, insisting that he wants to serve out his current term of office, which expires in 2013. The GCC plan proposes the formation of a government of national unity, Saleh transferring power to his vice president, and an end to the deadly protests in Yemen, the Arab world\'s poorest nation. The president would submit his resignation to parliament within 30 days, to be followed two months later by a presidential election.