BEIRUT - One person was injured in sectarian violence in the northern Lebanese port city of Tripoli overnight Thursday, a security official told AFP.

A passerby from the Sunni neighbourhood of Bab al-Tebbaneh was injured in the crossfire between fighters from his district and the neighbouring largely Alawite area of Jabal Mohsen, the official said on the condition of anonymity.

Alawites are a secretive off-shoot of Shiite Islam who revere Imam Ali, the cousin and son-in-law of the Prophet Mohammed.

Bab al-Tebbaneh, is a stronghold of the anti-Syrian parliamentary majority while the inhabitants of Jabal Mohsen are supporters of the Hezbollah-led opposition.

Three grenades had explode overnight on Thursday in those neighbourhoods where such incidents have become frequent despite an army presence meant to bring calm.

After the exchange of fire, gunmen from both sides maintained a presence in their neighbourhoods for the first time since the army deplyed in full-force in mid-July, pledging a tough response to any breach of security.

Repeated clashes between the two areas left 14 people killed and over 100 injured in since June.