BEIRUT (REUTERS) - A suicide bomb attack on a cafe in the Lebanese city of Tripoli killed at least seven people on Saturday, the latest violence to hit a region repeatedly buffeted by violence linked to the civil war in neighbouring Syria.

The army said the attack in the predominantly Alawite neighbourhood of Jabal Mohsen was carried out by one suicide bomber.

Lebanon's National News Agency said it was a double suicide bombing and gave the names of two attackers it said were from Tripoli.

Lebanon's Health Ministry put the death toll at seven but officials said nine people were killed, not including the bombers.

Three dozen other people were wounded in the attack.

The governor of northern Lebanon ordered a curfew until 7am in Jabal Mohsen and the army set up a security cordon around the cafe, the National News Agency reported.

The last major flare-up in the predominantly Sunni Muslim city of Tripoli was in October, when at least 11 soldiers and 22 militants were killed in fighting between Sunni Islamists and the army.

Lebanese security officials have repeatedly warned of plans by Islamic State and Al-Qaeda-linked militants in Syria to destabilise Lebanon.

Islamist militants staged an incursion into the border town of Arsal last August and are still holding captive 26 members of the security forces seized in the raid.

The targeted cafe was on a street dividing Jabal Mohsen from the Sunni district of Bab al-Tabbaneh, which has often turned into a front line for conflict between Sunni and Alawite communities over the years.

Health Minister Wael Abu Faour called for unity in Lebanon, whose sectarian divisions have been exacerbated by the war in Syria, where the Alawite-led government of President Bashar al-Assad is fighting an insurgency now dominated by Sunni Islamist groups including the Nusra Front and Islamic State.

"This is the moment for consensus among Lebanese to protect Lebanon," Abu Faour told New TV, a Lebanese television station.