NORTH SINAI, Jun 9 (Aswat Masriya) - Security forces targeted early Tuesday a group of "highly dangerous extremists" in North Sinai, killing five of them, a military source said.

The source said four of the killed suspected militants were plotting a "terrorist operation" against security forces in the Sheikh Zuweid region.

The fifth was gunned down while attempting to plant an explosive device east of al-Arish, the source added.

Twelve suspects were also arrested as part of the security campaign on North Sinai, the source said.

Unidentified gunmen had attacked a military checkpoint in Sheikh Zuweid with mortar shells late Monday, yet the attack left no injuries.

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 armed forces has launched an intensified crackdown in the Sinai Peninsula in response to the militancy.

Armed forces spokesman Mohamed Samir said last week that a total of 141 suspected militants have been killed in North Sinai in the month of May.