Occupied Jerusalem: A UN envoy said on Tuesday it could take the Lebanese army and international troops two to three months to fill a security vacuum in southern Lebanon and cautioned that fresh fighting could be sparked unintentionally.

Terje Roed-Larsen, an envoy on Syria-Lebanon issues, said the United Nations had asked Israel to refrain from using force directly to prevent Hezbollah fighters from rearming.

He said that doing so would violate a week-old ceasefire and undercut efforts to dispatch UN troops to southern Lebanon.

"The situation is still extremely fragile and extremely complicated and extremely dangerous ... Unintended incidents can kick off renewed violence, which might escalate and spin out of control," Roed-Larsen said.

Israeli officials say the Jewish state has the right to enforce the arms embargo if no one else will.

Israeli commandos attacked a Hezbollah strong-hold last weekend, prompting angry responses from the Lebanese government and the United Nations.

Roed-Larsen said the UN was "very explicit" with Israeli leaders that suspected arms shipments in violation of a UN embargo "must be handled by Lebanese authorities".

"It is not wise to conduct acts which constitute violations of the UN resolution," Roed-Larsen said. "It might run the risk of renewing the conflict".