The leader of an Islamic State affiliate in Egypt has vowed to kill judges and security forces in retaliation for the execution of six suspected militants earlier this week.

Abu Osama el-Masri, the leader of the group calling itself the Sinai Province, made his threat in an audio message posted Thursday on social networking sites.

"You have killed our brothers, enraged our hearts ... In the name of God, we will take revenge after (the execution of) our brothers from the sect that issued the ruling and the sect that executed it," he said.

On Sunday, Egypt executed six suspected Islamic militants convicted by a military court last year over the killing of two military officers during a raid north of Cairo in March 2014.