Egypt on Tuesday executed four alleged Islamic militants following their conviction by a military tribunal in the killing of three military academy students in a 2015 bomb attack that wounded six others./ABC News

The attack took place outside a stadium in the Nile Delta city of Kafr el-Sheikh as the military cadets were waiting for a bus to take them to the academy.

Egypt has struggled to combat an Islamic State-led insurgency based in the northern Sinai Peninsula that has claimed attacks across the country in recent years.

Tuesday's executions at a prison in the Mediterranean port city of Alexandria bring to 19 the number of convicted militants executed over the past week.

Authorities executed 15 militants on Dec. 26 after a military court convicted and sentenced them to death over a 2013 attack on a military checkpoint in the Sinai Peninsula. An officer and eight soldiers were killed in that attack.

Six militants were hanged in a separate terror case in 2015 after being convicted by a military tribunal.

Rights groups say the legal process is flawed. They decried last month's executions, arguing that at least one of the 15 was tortured in detention and that relatives were not allowed to see them on the day of their execution in accordance with regulations covering capital punishment.

The spate of executions follows an uptick in high-profile attacks and repeated vows by President Abdel-Fattah el-Sissi to use "brute force" to crush the insurgency.

On Friday, a militant killed at least nine people when he attacked a Christian church in a Cairo suburb and a nearby Christian-owned shop. The attacker was arrested and has been charged with murder and illegal possession of a firearm.

On Dec. 19, militants fired a guided rocket that damaged a helicopter at the airport of el-Arish during a previously unannounced visit by the defense and interior ministers to the Sinai coastal city in northern Sinai.

IS claimed both attacks.

In the deadliest attack by militants on civilians, 311 worshippers were killed inside a mosque in northern Sinai on Nov. 24. There was no claim of responsibility for the massacre, but witness accounts said the gunmen carried the IS group's black banner.