CAIRO, Aug 6: Gunmen killed 16 Egyptian policemen on Sunday and seized two military vehicles to attack a crossing point into Israel, the deadliest incident in Egypt’s tense Sinai border region in decades.

Israeli aircraft destroyed one of the armoured vehicles and four of the gunmen were killed, Egyptian security sources said.

Israel’s Defence Minister Ehud Barak called for “determined Egyptian action” to “prevent terror in Sinai”.

The attack is an early diplomatic test for Egyptian President Mohamed Mursi, an Islamist who assumed office at the end of June after staunch US ally Hosni Mubarak was overthrown last year in a popular uprising.

It may also complicate Egypt’s relations with Hamas, the Islamist rulers of the Gaza Strip who are close to Mursi’s Muslim Brotherhood, if it is shown that Palestinians were involved.

Muslim Brotherhood, the party to which Mohamed Mursi belongs, said on its website that the attack “can be attributed to Mossad”, the Israeli intelligence agency, and was an attempt to thwart the President.

The statement said Mossad was trying to abort the Egyptian uprising that toppled president Hosni Mubarak last year and that it was “imperative to review clauses” of the agreement between Egypt and Israel.

The gunmen first ambushed the Egyptian border police who had gathered for Iftar.

“Elements of a jihad organisation drove SUVs into one of the checkpoints south of the Ramah border,” Egyptian state television said, referring to the main Gaza-Egypt crossing point. It said 16 security forces personnel were killed and seven wounded.

One of the stolen army vehicles exploded as the militants tried to storm the Israeli border and the second was targeted by the Israeli air force at the Kermes Shalom crossing into southern Gaza, a military zone where the Israeli, Egyptian and Gaza borders intersect.

“As of now, we know of no terrorists still in the area. There are some Israeli communities nearby, and residents have been asked to stay in their homes,” an Israeli military spokeswoman said.

An Egyptian security source said the Ramah crossing had been closed “indefinitely” after the attack.

Israel has accused Palestinian militants in Gaza of involvement in militant activity in Sinai, where insecurity has grown since Hosni Mubarak was toppled.

President Mursi has pledged to get a grip on security in Egypt, but has yet to prove he can assert control over an entrenched security establishment.

Mursi summoned senior military officials and vowed to respond to the attack. His spokesman said the assailants had not been identified for now.

“Clear orders have been given to our armed forces and police to chase and arrest those who carried out this assault on our children,” Mohamed Mursi said in a speech on state television. “The forces will impose full control over these areas of Sinai.”

The Egyptian state news agency quoted a security official as saying the attack was carried out by Islamist militants who infiltrated from Gaza via a tunnel as well as by other militants from two regions in Egypt’s Sinai peninsula.

Hamas said it was investigating the incident and had no information so far indicating the gunmen came from Gaza, but Taher al Nono, a spokesman for the Hamas government, said it was closing tunnels along the border with Egypt immediately.

Israeli Prime Minister Benjamin Netanyahu said the Israel Defence Forces and members of the internal security agency had foiled a big attack against Israeli civilians.

“Whoever intends to attack us must know that our long arm will find him,” he said in a statement via Twitter.

Israeli Prime Minister Benjamin Netanyahu had said in April that Sinai was becoming a lawless “wild west”, but his government has since signalled more confidence in Egypt’s ability to restore order.

Jihadi groups have hidden out in the lawless Sinai for almost a decade, but security forces hemmed them in under Mubarak.

They became more active after Egypt’s uprising last year with attacks on security posts, military roadblocks and a key gas export pipeline and occasional raids on the heavily defended border with Israel.