NORTH SINAI, Jun 30 (Aswat Masriya) - A mortar shell of an unknown source hit a house near a security base in North Sinai's Sheikh Zuweid on Tuesday, killing two children, medical sources said.

The attack also left three injured, the sources told Aswat Masriya. They were transferred to the al-Arish General Hospital.

The bodies of two children and an adult were also found in Sheikh Zuweid, tribal sources said. The bodies contained signs of gunshot wounds, yet the causes of their death remain unknown.

The number of civilians killed in armed attacks by militants in North Sinai significantly surged during the past year. 

Residents of the Sheikh Zuweid region found on August 20, 2014 the decapitated bodies of four civilians.

In a video allegedly released in August by the Sinai-based Ansar Bayt al-Maqdis, the group claimed responsibility for the beheading of the four civilians, accusing them of providing intelligence to Israel.

Similar executions of civilians have been repeatedly occurring since then, gripping the lives of dozens of residents.

Militancy inside Egypt has seen a significant rise since the military ouster of Islamist president Mohamed Mursi in July 2013, which was prompted by mass protests against his rule. Most attacks occur in North Sinai, targeting security forces. The attacks have left hundreds of security personnel killed.

Ansar Bayt al-Maqdis is Egypt's most active militant group, having claimed responsibility for the majority of militant attacks in the peninsula. The group pledged allegiance to the Islamic State fighters in Syria and Iraq last November, changing its name to Sinai Province.