Militants of the Sinai Province group — a branch of the Islamic State of Iraq and Syria group (ISIS) — launched their biggest assault in years against Egyptian security forces on Wednesday. Dozens of people have been killed in the past few days of clashes.

Also on Saturday, a woman and two children were killed after a shell slammed into a house in North Sinai, medical and security sources told Agence France-Presse.

It was not immediately clear which side fired the shell in the North Sinai town of Sheikh Zuweid.

A woman and a teenage girl were also seriously wounded, the sources said.

The government called in air strikes on Wednesday after a spectacular ISIS attack in Sheikh Zuweid.

The army said 17 soldiers and 100 militants had been killed. But medical and security officials said the death toll was at least 70 people — mostly soldiers — as well as dozens of militants.

The violence poses a major test for Sisi, the former army chief who has pledged to eliminate the militants.