* Two Sunni suicide bombers kill 13 soldiers in Rahjan
* Attack unusual in Sunni hometown of defence minister (Adds rebel statement, suicide bomber's final message)
BEIRUT, Jan 28 (Reuters) - Two suicide bombers, one from an al Qaeda-linked rebel group, killed 13 soldiers in an attack on the Syrian defence minister's hometown, rebels and an opposition monitoring group said on Tuesday.
The Syrian Observatory for Human Rights said a well-known Saudi militant who came to Syria to fight with the country's al Qaeda affiliate, the Nusra Front, was one of the fighters who blew himself up late on Monday at an army checkpoint in the village of Rahjan in the central province of Hama.
Syria's nearly three-year conflict began as peaceful protests against President Bashar al-Assad's rule but has devolved into civil war that has killed more than 130,000 and brought violence to every region.
Rahjan, in a remote eastern part of Hama, is the ancestral home of Defence Minister Fahd al-Freij, who is now living in the capital Damascus.
"This is a message from the Nusra fighters to Freij: 'You cannot protect your own relatives,'" said Rami Abdelrahman, head of the Observatory, a Britain-based group with a network of sources across Syria.
Another Islamist rebel group, Ajnad al-Sham, also claimed participation in the Rahjan attack. In a statement, it said the town was targeted because it was the largest base for pro-Assad militias in the area.
Freij is a Sunni Muslim and Rahjan is largely Sunni, another reason the attack by Sunni militants was unusual in a civil war that has become increasingly sectarian and drawn foreign militants to join the opposing sides.
The uprising has been led by Syria's majority Sunnis. Assad is from the minority Alawite sect, an offshoot of Shi'ite Islam, and has been largely supported by Syrian minorities.
Shi'ite groups such as Lebanon's Hezbollah are helping Assad. But some Sunnis, such as Freij, continue to back Assad.
Abdelrahman said the attack by the suicide bombers, who detonated their explosives-rigged cars, sparked clashes around Rahjan between the army and rebels that raged until dawn on Tuesday. Five Nusra fighters and were killed as were three combatants from other rebel groups, he said.
The Saudi suicide bomber who died in the attack, Turki al-Ashaari, was well known by Islamists on social media websites.
His last post on his Twitter account cited "the last chapter of my life" and linked to two statements, with messages to his family, al Qaeda leaders and his fellow fighters.
"You should carry out martyrdom operations. Your souls are cheap, not expensive. All you must do is be sure you are killing apostates. Do not place yourself in a suspicious place," he said in one statement. "I seek martyrdom and the house of Assad will be destroyed with me." (Reporting by Erika Solomon; Editing by Mark Heinrich)