Even as Egyptian government sources branded the Islamist gunmen who killed 16 policemen in Sinai near the Israeli border Sunday as "infidels," President Mohamed Morsi's Muslim Brotherhood party said on its website that the attack "can be attributed to Mossad" and was an attempt to challenge Morsi's administration.

An Egyptian official said that insurgents had crossed into Egypt from the Gaza Strip before attacking the police station Sunday, Reuters reported. The attackers then headed to Israel, where they were killed by Israeli fire.

In an effort to assert its control over the lawless Sinai Peninsula, which Israel returned to Egypt under the 1979 peace treaty by which the latter agreed to leave the area demilitarized, Egypt vowed Monday to take on the Islamist militants in the region.

Israeli defense official voiced their willingness to consider any Egyptian request to deploy additional military forces in the Sinai in an effort to retake control of the peninsula from the clutches of the Jihadists, the Jerusalem Post reported.

"The armed forces have been careful in the past months and during the events of the revolution not to shed Egyptian blood," the Egyptian military said in a statement. "But the group that staged this attack is considered by the armed forces as enemies of the nation who must be dealt with by force."

"There is a red line and passing it is not acceptable. Egyptians will not wait for long to see a reaction to this event," the statement said.

However, Egypt's Brotherhood said Mossad, the Israeli intelligence agency, was attempting to abort the Egyptian uprising which toppled the longstanding Hosni Mubarak's regime and culminated in the swearing in of Morsi.

"This crime can be attributed to the Mossad, which has been seeking to abort the revolution since its inception and the proof of this is that it gave instructions to its zionist citizens in Sinai to depart immediately a few days ago," the Brotherhood said in its website, as reported by Reuters.

"(It) also draws our attention to the fact that our forces in Sinai are not enough to protect it and our borders, which makes it imperative to review clauses in the signed agreement between us and the zionist entity," the group said.

Israel dismissed the allegation as "nonsense."  "Even the person who says this when he looks at himself in the mirror does not believe the nonsense he is uttering," Foreign Ministry spokesman Yigal Palmor said.

The Hamas government and some Palestinian groups have also hinted at Israel's involvement in the attack which was allegedly aimed at developing friction between the Palestinians and the new Egyptian government.

A Hamas government spokesperson said the attack was Israel's "attempt to tamper with Egyptian security and drive a wedge between the Egyptians and the residents of the Gaza Strip."

"This is a despicable crime that only serves the interests of the Zionist enemy," a Hamas spokesman was quoted as saying by Jerusalem Post. "We believe that Israeli agents were behind the attack."

Hamas officials maintained that none of the insurgents were from Gaza, but didn't say who they thought was responsible for the attack.