Police in Israel say an armed Palestinian has breached security at Britain's embassy in Tel Aviv and is demanding asylum.

Israeli media reports say the man, from the West Bank town of Ramallah, infiltrated the embassy's parking lot Thursday and threatened to kill himself if Britain does not grant him asylum.

Israeli security forces have taken up positions around the embassy.

News reports say the man claims to have been an informer for Israel's security service, Shin Bet.

In the Israeli-occupied West Bank, Palestinians say Israeli troops killed a commander of the Palestinian al-Aqsa Martyrs Brigades during a brief firefight in Nablus early Thursday.

In other news, the Israeli army says it is withdrawing from the outskirts of Gaza City.

Palestinian witnesses say at least 18 people have been killed in Israeli air strikes and artillery fire since Israeli forces entered the area Saturday.

The army said on Wednesday that searches in a section of the city turned up a 150-meter-long underground tunnel leading to the Karni crossing point into Israel.

Also on Wednesday, U.N. Secretary-General Kofi Annan called for an end to Israel's offensive in the Gaza Strip, which began in late June.

Mr. Annan spoke after meeting with Palestinian President Mahmoud Abbas in Ramallah.

Some information for this report was provided by  AP and Reuters.