BEIRUT - Two suicide bombers from al-Qaida-linked groups blew themselves up at an army post in the Syrian town of al-Nabak on Wednesday, halting an advance by President Bashar Assad's forces near the Syrian-Lebanese border, activists said.The battles raging around the Qalamoun range spanning Syria and Lebanon are part of a much-anticipated offensive by Assad's forces to secure a highway linking Damascus to the province of Homs and thus consolidate their grip on central Syria.The Syrian Observatory for Human Rights said suicide bombers attacked the army checkpoint in explosive-laden cars, killing and wounding several soldiers, but gave no precise toll.The British-based monitoring group said the blasts coincided with a rebel attack on the nearby government-held town of Deir Attiya, which had not previously been involved in the fighting.