EL-ARISH, Egypt—Egyptian security forces on Thursday arrested a militant wanted in connection with a deadly attack earlier this year on police and military officers in the restive Sinai Peninsula, officials said.

Ahmed Allam el-Hefny was detained in the town of Sheikh Zuweyid near the city of el-Arish in northern Sinai, security officials involved in the raid said on condition of anonymity because they aren't authorized to brief the media. In September, el-Hefny was convicted in absentia and sentenced to life in prison for a June 2011 attack on el-Arish's main police station and a bank. Because he was tried in absentia, he will be given a retrial now that he is in custody.

The arrest marked a small victory for Egypt's embattled security forces in northern Sinai, where militants have regularly ambushed police checkpoints and also staged cross-border strikes into neighboring Israel. In the past week alone, suspected Islamic militants have killed three policemen and wounded a third—violence that led to the sacking of the security chief and a rare protest by policemen to demand better equipment and a more sweeping military crackdown on the extremists.

The number of attacks has multiplied since last year's popular uprising that toppled longtime autocrat Hosni Mubarak and caused security in the area to deteriorate. In August, militants killed 16 Egyptian soldiers near the border with Israel, while in two months later gunmen opened fire on Israeli soldiers near the border, killing one.

Egypt's military launched an operation in Sinai following the deadly August attack, although the campaign has yielded few tangible results. Israel quietly agreed to allow several thousand Egyptian soldiers into Sinai to secure the peninsula, despite limitations imposed by the 1979 peace treaty between the two countries.

On Wednesday, police said they arrested three other suspected extremists. Officials said they found the uniform of a high ranking military officer with one of the men.

Ansar Jerusalem, an al-Qaida-inspired group that is hostile to both Israel and Egypt, released a video Wednesday about one of its fighters who was killed in August in a strike that Egyptian officials said at the time may have been carried out by Israel. The group said the man participated in a cross-border attack in August 2011 in Eilat, Israel, that killed eight people.

In the video, a Bedouin confesses to working as a spy for Israel for $3,000 a month and to placing an electronic chip on the militant's motorcycle. He also says that Israeli intelligence officers crossed into Sinai several times and planted a bomb on the road leading to the militant's home. Pictures are then shown of the Bedouin man's severed head.