Israeli authorities on Monday barred two Moroccan MPs accompanying EU parliamentarians from crossing into the West Bank to meet Palestinian officials, one of the lawmakers said.

"The Israel authorities prevented me and my colleague Ali Salem Chekkaf from crossing into the West Bank without giving us any reason," Mehdi Bensaid told Agence France Presse.

Pro-Palestinian activists said on Monday they would not withdraw a lawsuit against Israeli commanders for a fatal 2010 raid on their Gaza-bound flotilla, ahead of official compensation talks between Turkey and the Jewish state this week.

"We will not discuss compensation or give up on the trials until the blockade over Gaza is removed," said Musa Cogas, one of the activists who was on board the Mavi Marmara, the largest ship in the flotilla aimed at breaking Israel's Gaza blockade.

Sirens wailed across Israel on Monday, bringing millions of people to a halt for two minutes as they remembered the six million Jews who were killed during the Nazi Holocaust.

The annual ritual, which takes place at 10:00 am (0700 GMT), is a central part of Holocaust Memorial Day which began at sundown on Sunday.

Israel shut a crossing with Gaza after rockets were fired from the Hamas-ruled territory at the Jewish state on the day it commemorated the Holocaust.

The military said it closed the Kerem Shalom terminal Monday. Another crossing would be open for humanitarian cases only, it said.

Israeli Prime Minister Benjamin Netanyahu said Sunday that Israel cannot rely on any other country, even an ally, when it comes to facing up to the perceived nuclear threat from Iran.

"We appreciate the efforts of the international community to halt Iran's nuclear program," Netanyahu said in a speech on the eve of Holocaust Day.

A rocket fired from Gaza crashed into southern Israel on Sunday, without causing casualties or damage, shortly after the arrival of U.S. Secretary of State John Kerry on a peace bid, police said.

Police spokesman Micky Rosenfeld told Agence France Presse the rocket landed in an uninhabited sector of the Negev desert, as Kerry started a three-day visit to Israel and the Palestinian territories.

Israel's lead peace negotiator Tzipi Livni on Sunday ruled out Turkey taking an immediate role in reviving talks with the Palestinians, shortly before U.S. Secretary of State John Kerry flew in.

Asked if Turkey could play an important role in the peace process -- an idea raised by Kerry at a press conference earlier in the day in Istanbul -- she told public radio: "The idea is interesting, but it could take time."

Vandals scrawled Hebrew threats on two mosques in a West Bank village in the latest hate crime by suspected Jewish extremists, a local official said on Sunday.

"Settlers came in the middle of the night and wrote threats in Hebrew on the walls of two mosques and slashed the tires of a car," said Adel al-Shaer, a councilor for Teqoa village east of Bethlehem.

The United States' top diplomat warned Iran on Sunday that time is running out on nuclear negotiations between the Islamic republic and world powers.

"This is not an endless process. ... You can't just talk for the sake of talking," Secretary of State John Kerry told a news conference in Istanbul.

Hackers launched a massive international cyber attack campaign against Israeli government websites on Saturday and Sunday, amid numerous threats from the Anonymous hacker collective.

The global hacker group had promised a mass assault to protest Israeli policy toward the Palestinians. The attack appeared timed to coincide with Israel's annual Holocaust memorial day, beginning at sundown Sunday.