NORTH SINAI, Egypt - At least two policemen were killed in an armed attack by extremists in Egypt's North Sinai, a security official told Xinhua on Friday.

"The gunmen are believed to belong to Islamist Jihadists," the source said, noting that the gunmen riding a bike opened fire at the Egyptian police stationed in Al-Masaeed town in the west of Arish city, capital of North Sinai.

Nine extremists have been arrested in Arish and the military helicopters are combing the area, said the source.

Tarek Khater, undersecretary of health ministry in North Sinai, told Xinhua that at least 20 were injured in clashes between supporters of ousted president Mohamed Morsi and security forces outside the governorate headquarters in Arish.

Earlier on Friday, one soldier was killed and three others injured in North Sinai when hundreds of gunmen attacked Arish Airport, a security camp in Rafah, a police station and two security checkpoints in Sheikh Zuwaid by heavy artillery and rocket-propelled grenades.

The attacks came after the Egyptian army ousted Islamist- oriented president Morsi on Wednesday in response to millions of protesters who took to the streets and public squares across the country demanding his removal.

Islamist supporters of Morsi rejected the ouster as "a military coup" and vowed to struggle for Morsi's legitimacy.

In Cairo, at least three people were killed and dozens injured on Friday outside the Republican Guards House, where Morsi is reportedly under house arrest, during clashes between security forces and Morsi's advocates.