Defense Minister Moshe Ya’alon on Monday gave permission for Egypt to deploy two infantry battalions in the Sinai region, in the el-Arish and Rafah areas.

The new forces will join a large number of Egyptian troops already operating in the area, carrying out a major crackdown on terrorist activity, in an agreed departure from the 1979 Israel-Egypt peace agreement that states the peninsula should remain demilitarized.

Egypt submitted a formal request to the Defense Ministry in Tel Aviv to send in the extra troops. Ya’alon reviewed it, and approved it.

The additional forces mean that Egypt now has 11 infantry battalions deployed in the Sinai, as well as a tank battalion and assault helicopters — all emplaced with Israel’s formal approval, as required by the treaty.

The crackdown marks the first truly effective Egyptian operation against the Sinai terror groups, an informed source in Jerusalem told The Times of Israel on Monday.

A problem since the fall of president Hosni Mubarak two years ago, the situation has deteriorated even further since the removal of president Mohammed Morsi earlier this month.

Israel’s approval came a day after two masked gunmen opened fire on IDF soldiers from across the border on Sunday.

Earlier Monday, at least three people were killed and 17 wounded in northern Sinai when terrorists fired rocket-propelled grenades on a bus carrying workers en route to work at a cement factory in el-Arish.

In the past two weeks, at least eight Egyptian security officers have been killed in battles with gunmen, the most recent on Friday. Two Christians have also died, one a priest. A gas pipeline to Jordan was bombed, ending a lull in such strikes.

Last Wednesday, gunmen opened fire on the convoy of the commander of the 2nd Field Army, who escaped, but a 5-year-old girl was killed in the subsequent gunbattle.

Egyptian army spokesman Col. Ahmed Mohammed Ali told Asharq al-Awsat on Friday that “terrorists have escalated their planned operations against the police and armed forces in the Sinai over the last few days. Their aim is to spread chaos and undermine Egyptian national security.”

The military and security forces have widened their presence, and in the past two weeks maintained a campaign to destroy hundreds of smuggling tunnels between the Sinai and Gaza, putting them almost entirely out of commission.

Cairo was concerned that some of the armed elements operating in Sinai would find refuge in the Gaza Strip and that they would use the subterranean smuggling tunnels running beneath the shared border — a key economic component of Hamas rule in Gaza — to evade Egyptian authorities.

Sinai has been the most lawless corner of Egypt since the ouster of Mubarak in early 2011. Police stations have been torched and security forces kicked out of tribal areas where they were notorious for abuses. Shootings took place regularly on police and military outposts.

In a particularly bloody incident last August, just a month after Morsi took office, gunmen killed 16 Egyptian soldiers, commandeered armored vehicles and attempted to drive into Israel to carry out an attack there. Israel stopped one vehicle at the border, and destroyed the second in an air strike when it was already inside Israel. The Egyptian military responded with a major security operation in Sinai.

Since the military deposed the Islamist president on July 3, militant groups have lashed out with increased violence.