Local officials said the attack was carried out on Monday night by Syrian war planes that fired at an area in the Arsal region of Lebanon, which has regularly been targeted by cross-border strikes.
In a statement, Sleiman said "an ambulance was targeted by Syrian rockets" and called for humanitarian bodies to be protected from "conflict and hostilities".
Local officials confirmed the attack.
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"Syrian war planes targeted an ambulance in the Wadi Hmeid area of Arsal, but there were no injuries," an official told AFP on condition of anonymity.
A security source said war planes had fired five rockets in the attack.
The Arsal area is mainly Sunni, and is broadly supportive of the Sunni-dominated uprising against Syrian President Bashar al-Assad.
The mountainous area has long been a smuggling haven, with multiple routes into Syria that have been used since the conflict began in March 2011 to transport weapons and fighters.
Syria's conflict has polarised Lebanon, with Sunnis largely backing the uprising, and Shiites, including the powerful Hezbollah movement, backing Assad's regime.