Jan. 23 (Bloomberg) -- Hamas militants blew 15 holes in a security fence separating the Gaza Strip and Egypt, enabling thousands of Palestinians to leave the blockaded enclave to search for food and supplies.

After detonating bombs along the fence at about 4 a.m. local time today, militants used bulldozers to remove barbed wire and concrete emplacements, witnesses said. By late afternoon, as many as 350,000 people, a fifth of Gaza's population, had crossed into Egypt, Israel's Haaretz daily said, citing the United Nations.

``In addition to visiting my sick sister in Egypt, I want to buy some stuff to bring back to Gaza,'' Mufida Abu Zarqa, 52, said as she and her three daughters entered a breach in the fence. ``Because of the closure, we lack a lot of things, like food, fuel and cigarettes.''

Israel has gradually tightened a two-year blockade of Gaza, with some Egyptian cooperation, in an effort to weaken Hamas and end rocket attacks by Gaza militants. The Islamic movement, which is designated a terrorist organization by the U.S. and the European Union, is sworn to the Jewish state's destruction.

U.S. `Concerned'

David Welch, the U.S. assistant secretary of state for the Middle East, spoke yesterday and today with Egyptian Ambassador Nabil Fahmy in Washington, State Department spokesman Tom Casey said. The U.S. Embassy in Cairo also has been in contact with Egyptian officials there, Casey told reporters in Washington today.

``We're concerned about that situation and, frankly, we know the Egyptians are as well,'' Casey said. ``I think they're doing what they can under the circumstances.''

The border crossings stem from Hamas's ``illegal actions in Gaza, their unwillingness to behave in a responsible manner,'' Casey said. ``We're going to continue to work with the Egyptians and others on this.''

On Jan. 17, Israel banned all shipments across Gaza's borders, a move that Palestinian officials said has forced the enclave's sole power station to shut down for almost a day after it ran out of fuel and exacerbated shortages of basic goods.

Palestinians flooding over the border went in search of food, medicine and cigarettes in Egypt, all in short supply in the 360-square-kilometer (144-square-mile) Gaza Strip. Gaza City's streets were mostly empty as residents headed toward the Rafah border crossing in cars, trucks and buses.

Smuggling Feared

Israel's government said it was concerned that militants would use the breach in the border fence to bring arms and terrorists into Gaza.

``We have real concerns that they can now freely smuggle explosives, missiles and people into Gaza, which makes an already bad situation even worse,'' Israeli Foreign Ministry spokesman Aryeh Mekel said in a telephone interview from Jerusalem. ``Egypt should take care of the problem.''

Hamas called on Egypt and Palestinian Authority President Mahmoud Abbas, leader of the Fatah movement, to join the group for ``urgent'' talks about formally reopening the crossing between Gaza and Egypt. Negotiations should be aimed at establishing a mechanism for joint control of the border, Hamas leader Ismail Haniya said in an e-mailed statement.

Palestinian Authority

``The Palestinian Authority is prepared to play its role to make sure that there's a solution to this crisis,'' the authority's prime minister, Salam Fayyad, said today in a joint news conference with German Foreign Minister Frank-Walter Steinmeier in Berlin. The blockade ``will only lead to further suffering on the part of people in the Gaza Strip,'' Fayyad said.

Fatah and Hamas ended a coalition government in June after Hamas seized the Gaza Strip, leaving Fatah in control of the West Bank. Haniya maintains he is still Palestinian Authority prime minister, though Abbas formed an emergency government and named Fayyad to lead the Cabinet.

At the Rafah crossing, international broadcasters aired coverage of Egyptian security guards exchanging fire with Palestinian militants today. No injuries were reported.

Egyptian President Hosni Mubarak said he ordered his country's forces to allow the Palestinians to enter because they were starving, the Associated Press reported. ``I told them to let them come in and eat and buy food, and then return them later as long as they were not carrying weapons,'' AP cited Mubarak as saying in Cairo.

Israel denies that Gaza faces a humanitarian crisis as a result of the stepped-up sanctions.

Security Council

The United Nations Security Council met yesterday in emergency session to discuss the situation in Gaza. The Palestinian envoy to the UN, Ambassador Riyad Mansour, told the council the blockade was undermining U.S.-backed efforts to get a peace agreement between Israelis and Palestinians.

UN Secretary-General Ban Ki-moon telephoned Israeli Prime Minister Ehud Olmert on Jan. 21 to express concern about the situation, the UN said.

Israeli troops killed a Hamas militant and wounded four others in clashes in Rafah late yesterday, Mo'aweya Hassanein, head of emergency medicine at the Palestinian Health Ministry, said in a phone interview. He said a second Palestinian, identified as a farmer, was killed in northern Gaza.

A spokeswoman for the Israel Defense Forces, commenting anonymously by regulation, confirmed that a soldier hit a Palestinian in a firefight and said she knew nothing about the second incident.

To contact the reporters on this story: David Rosenberg in Jerusalem at drosenberg1@bloomberg; Saud Abu Ramadan in Gaza City through the Jerusalem bureau at .

Last Updated: January 23, 2008 13:13 EST