buses as they headed towards the town of Rafah on the border with the

Palestinian Gaza Strip.

The attack was the deadliest in the Sinai in years, exceeding the toll from an August 2012 attack on Egyptian soldiers that killed 16.

The security situation in the Sinai Peninsula, which borders both Gaza and Israel, has deteriorated since 2011, when president Hosni Mubarak was overthrown.

But it has become significantly worse since the army ousted president

Mohamed Morsi on July 3, with near daily attacks by militants targeting police and military installations.

According to an AFP tally, at least 49 security officials have been killed in Sinai since July 5th -- 28 police and 21 soldiers -- not including those in the latest attack.

Egypt has deployed additional forces to Sinai, which is mostly desert and inhabited by Bedouin tribes that have been accused of cooperating with Islamist militants.

The army says it has killed nearly 70 "terrorists" in the region since July 3.

The violence comes as Egypt wrestles with a deep political crisis and

bloodshed that has left hundreds of people dead in days of clashes between Islamist protesters and security forces.