* One dead, 37 hurt at checkpoint on Beirut-Damascus highway
* Security chief passes checkpoint minutes before blast
* Bekaa Valley region has been drawn into Syria conflict (Adds Hezbollah reaction, security official)
By Laila Bassam
BEIRUT, June 20 (Reuters) - A suicide bomber killed one person and wounded 37 in an attack at a security checkpoint in Lebanon on Friday that narrowly missed a top security official who said he had been told Islamist militants wanted to assassinate him.
The explosion occurred in the country's Bekaa Valley near the Syrian border, an area where Lebanese Sunni Muslim militants opposed to Syrian President Bashar al-Assad have been targeting his key Lebanese ally, the Shi'ite Muslim Hezbollah movement.
The security official, Major General Abbas Ibrahim, said he passed through the checkpoint on the main highway between Beirut and Damascus minutes before the bomber blew himself up, just 200 metres (yards) away from his convoy.
"We miraculously escaped," Ibrahim told Reuters, adding that many officials in Lebanon were being targeted by the reactivation of "terrorist sleeper cells".
"But the security services are ready and on alert to stop them and we won't become another Iraq," he said in reference to the fighting between Shi'ite and Sunni factions in Iraq, where Sunni militants have seized wide swathes of territory.
Ibrahim, a Shi'ite who heads Lebanon's Directorate of General Security (DGS), said security officials had information that Sunni militants were aiming to assassinate him.
"We were suspicious of the (bomber's) car when we were on our way and when the car stopped at the Dahr al-Baydar checkpoint, the explosion went off," he said.
The dead man was a police officer at the checkpoint. The wounded were mainly police, as well as civilians, in the area.
On Friday security forces closed a number of roads in Beirut and Tripoli in anticipation of a security risk.
"Since this morning we have had strict security measures in Beirut and all areas because we had particular information," the head of Lebanon's internal security forces, Major General Ibrahim Basbous, said on Lebanese television.
SPILLOVER FROM SYRIA'S CIVIL WAR
The intensified security measures are part of an effort to contain spillover from Syria's civil war where Hezbollah fighters have helped Assad wrest back territory from mainly Sunni insurgents over the past year.
"The hand of terrorism has returned, extending over Lebanon, its security institutions and forces," Hezbollah said in a statement after the checkpoint attack.
Syria's conflict has re-aggravated sectarian strife in Lebanon where gunbattles, car bombs and rocket attacks linked to Syria have killed scores of Lebanese and revived memories of the country's own 15-year civil war that formally ended in 1990.
Sunni militants are angry with Hezbollah's intervention in Syria to bolster Assad, a fellow ally of Shi'ite Iran. Some Lebanese Sunnis have meanwhile joined the Syrian rebels.
The Shi'ite-dominated Bekaa valley has been frequently targeted by militants. A suicide bomber killed three people there in March and rockets struck a mainly Shi'ite town near the Syrian border later that month.
At the checkpoint where Friday's attack occurred, Lebanese television showed a charred vehicle and black smoke rising and debris littering the ground. Police said the bomber was stopped to be searched and then detonated his explosives belt.
The bomber used around 20 kg (42 pounds) of explosives, a local official at the Dahr al-Baydar checkpoint told reporters in footage on Lebanese television, adding that forensic and military experts were examining the scene.
Security sources said the DGS had received intelligence that groups under the leadership of the Sunni Islamist Abdullah Azzam Brigades, who are affiliated with al Qaeda, were planning to kill Ibrahim with a car bomb.
Lebanese police have begun rounding up people they suspect of links to al Qaeda and other militant groups.
Police said they arrested a group of suspected militants in a raid on a hotel in Beirut on Friday and they included foreigners and one Lebanese. They also detained a top commander linked to al Qaeda on Thursday in another raid. (Additional reporting by Reuters Television, Writing by Sylvia Westall; Editing by Samia Nakhoul and Mark Heinrich)