A small bomb went off near a UN peacekeeping vehicle in south Lebanon on Monday, causing no casualties, witnesses and UN officials said.

Witnesses said the blast detonated near the Qasmiyeh bridge on the main coastal road north of Tyre, where UN military police have an observation post near a Lebanese army checkpoint.

The explosion caused limited damage to a UN four-wheel drive vehicle. A Lebanese security source said the military police unit involved was from Tanzania.

"We can confirm an explosion occurred in the area of the Qasmiyeh bridge involving one UNIFIL vehicle," said the deputy spokeswoman Yasmina Bouziane for the United Nations Interim Force in Lebanon (UNIFIL), adding that no casualties had been reported. UNIFIL investigators had gone to the scene.

A car bomb killed six members of UNIFIL's Spanish battalion in the south on June 24. No group claimed responsibility for that attack, but the Spanish government said it suspected it was the work of al Qaeda-inspired Islamist militants.

UNIFIL has grown to 13,300 troops and naval personnel from 31 countries under a UN Security Council resolution that halted last year's conflict between Israel and Lebanese Hezbollah guerrillas.

The UNIFIL troops operate alongside some 15,000 Lebanese soldiers who deployed in the south after the July-August war.