Plainclothes security forces in Egypt have attacked anti-government demonstrators in the capital, Cairo, and the northeastern city of Port Said.

In Cairo, a demonstration turned violent on Sunday after the security forces began to remove tents and evict protesters from the Tahrir Square, where sit-ins have been held since November 22, 2012.

A group of protesters also blocked a major street leading to the Cairo International Airport, which led to a delay in the departure of visiting US Secretary of State John Kerry.

In Port Said, a policeman was killed and an Egyptian army officer was injured during clashes on Sunday.

The clashes erupted after the Egyptian Interior Ministry announced a decision to move nearly 40 prisoners who are waiting for a verdict over alleged involvement in a fatal football riot in 2012.

The verdict for the 39 defendants is set to be delivered on March 9.

In January, a court in Egypt sentenced 21 people to death for their role in the soccer disaster.

The verdict led to violent clashes that claimed the lives of at least 40 people.

On Sunday, over 250 people were also wounded in the clashes in Port Said, the Egyptian Health Ministry said. Police fired tear gas to disperse the angry protesters.

Unrest has gripped Egypt over the past few months. Egyptian protesters want President Mohamed Morsi to pursue the goals of the revolution that toppled former dictator Hosni Mubarak in 2011.

On March 1, clashes between police and protesters in the Nile Delta province of Dakahliya left at least one person dead and dozens of others injured.