Egyptian security forces on Wednesday launched airstrikes in the Sinai Peninsula, for the first time since the October war of 1973,  targeting extremist groups. More than 20 were killed in several areas of the governorate shortly after assailants opened fire on three joint military-police checkpoints.

Many checkpoints, especially in the city of Arish, saw exchanges of fire. Egyptian security troops and helicopters were reported to be combing the eastern area of El-Halal Mountain, hunting for armed insurgents, according to state-run Ahram news website.

The attacks of three joint military-police checkpoints late on Tuesday night  in response to a deadly attack on Sunday on a police station, which left at least 16 Egyptian police officers have been killed and others wounded in north Sinai on the border between Egypt and Israel, authorities say.

Exchanges of fire lasted until the early hours of Wednesday before armoured vehicles were sent in an attempt to contain the situation, Al Ahram reported.

The northern parts of Sinai have sunk into a state of lawlessness since last year’s  uprising that ousted former president Hosni Mubarak.

No one has yet claimed responsibility of the terror attack.

The Muslim Brotherhood has blamed  Israel’s intelligence agency Mossad of carrying out the attack to “hinder Egypt’s progress.”

Hamas and Israel have both distanced themselves from the attack, which the latter’s defence minister Ehud Barak said hoped would serve as a “wake-up call” to Egypt, which has been struggling to assert control over the Sinai peninsula.

Egyptian president Mohamed Mursi declared three days of mourning for the slain border guards.  The Egyptian military strikes came a day after the military held a funeral for the 16 soldiers killed in Sunday’s attack.  Mursi did not attend the funeral, where some protesters chanted slogans against the Brotherhood and even heckled Prime Minister Hisham Qandil.