Israel's Shin Bet security service has created a unit to focus on what it said was the growing terrorist threat from Egypt's Sinai desert.

Shin Bet officials said the peninsula was a hub for the global jihad movement with 15 Salafi groups alone operating in the area.

Four of them - Ansar Jerusalem, Mujahideen Sura Council in the Environs of Jerusalem (MSC), Jaish al Islam and Al Takfir Wal Hijra - were active in attacking the Israel Defence Forces (IDF) along the border and firing rockets into Israel.

According to Haaretz, the MSC had fired rockets at Eilat a number of times. It was blamed for killing an Israeli civilian working on the border fence in June 2012.

Al-Takfir was responsible for the August 2012 attack that left 16 Egyptian policemen killed. Jaisha al-Islam, which translates as Islam's Army, was involved in kidnapping soldier Gilad Shalit.

Shin Bet's reports differ from those of Israel's military intelligence. The security service estimated the number of operatives at several hundred people, while the military put it at a few thousand.

One of the key factors in the proliferation of Salafi groups in the past three to five years, which forced the two intelligence agencies to reorganise, was the Islamisation of once-secular Sinai Bedouin. Another factor was Israel's 2005 withdrawal from Gaza, allowing the region to export Palestinian fighters to Sinai - rather than the other way round.

Gaza has become a base for Salafis seeking military training, then going to the Peninsula, Syria and Yemen. The camps are run by the head of Jaish al-Islam, Mumtaz Dughmush.

"We thought Sinai was the source of all evil for Gaza, but it turned out that things were exactly the opposite," a senior intelligence official told Haaretz. "The Egyptians understood the situation much faster than we did."

Intelligence sources said they are satisfied with the levels of coordination with their Egyptian counterparts, but there is still a feeling that "the Egyptians are acting hesitantly against the Sinai Salafis and are afraid to confront them directly".

Twenty-five Egyptian policemen were killed in an ambush close to the Sinai town of Rafah, on the Gaza border, on Monday.

Egyptian deployments in Sinai are subject to the 1979 peace treaty between Israel and Egypt.