Egyptian President Abdel-Fattah el-Sissi returned to the capital Cairo early from an African Union summit in Ethiopia's capital Addis Ababa on Friday, in response to Thursday's simultaneous attack in Sinai.

At least 26 people, most of them soldiers, were killed in a series of simultaneous bombings and mortar attacks targeting a military base, a hotel, a police club and several checkpoints in the troubled Sinai Peninsula on Thursday. The most deadly attacks occurred in the North Sinai provincial capital, el-Arish. The nearby town of Sheik Zuwayid and the town of Rafah bordering Gaza were also targeted.

A militant group which in November changed its name to Sinai Province, or Waliyat Sinai, after pledging allegiance to the extremist organization "Islamic State," claimed responsibility via Twitter. They called it "an extensive simultaneous offensive for the soldiers of the caliphate." The group was previously known as Ansar Biet al-Maqdis (Partisans of Jerusalem).

In another incident, a suspected militant was killed while trying to plant a bomb in Port Said and a police officer was struck by a bomb in the canal city of Suez.

Thursday's attacks were the deadliest since October and occurred despite tough security measures in place since then, including the building of a buffer zone along the border with the Gaza Strip.

Violence despite crackdown

Jihadists have regularly targeted security forces in the Sinai Peninsula since July 2013, when then-president Mohammed Morsi was ousted by el-Sissi. The army chief-turned-president has overseen a stringent crackdown on the Muslim Brotherhood, which supported Morsi.

Egypt has seen a surge in violence and protests during the past week, as commemorations surrounding the anniversary of the January 2011 uprising against former longtime leader Hosni Mubarak turned deadly.

About 100 women gathered in downtown Cairo on Thursday to protest the fatal shooting of activist Shaimaa el-Sabbagh as well as other victims who were killed while attending a Saturday demonstration.

se/gb (AP, AFP, Reuters, dpa)