Police and military surround Abbasiya Square to stop clashes (Twitter)

Leading Islamist candidates in Egypt's presidential race have suspended their campaign over the authorities' handling of an anti-SCAF ( Supreme Council for Armed Forces) protest in Cairo in which 15 people have been killed.

According to activists, "army-sponsored thugs" attacked a camp in Abbasiya Square near the Defence Ministry where demonstrators were protesting against the disqualification of Salafi leader Hazem Salah Abu-Ismail from May's presidential race.

An Egyptian doctor volunteering at a field hospital in the area told the al-Dastour newspaper that at least 15 people have been killed and hundreds of others wounded in the clashes. The Interior Ministry confirmed 11 people dead.

The Muslim Brotherhood's Freedom and Justice Party (FJP) announced that it would boycott a planned meeting with the military council because of the clashes. There are rumours that the meeting will include a suggestion from SCAF to postpone the upcoming elections.

The April 6 Youth movement, which played a key role in the 2011 uprising that toppled president Hosni Mubarak, announced that one of its members, Ibrahim Abu El Hassan, had been killed in the clashes.

Protesters said they had held some of the thugs who attacked their camp overnight with cement-based bombs, stones, Molotov cocktails, birdshot and teargas canisters. They claim to have found army headquarter meals with the assailants - proof of a military connection, they said.

Activists confirmed that live ammunition has been used in the attack.

Police and troops were surrounding the area around Abbasiya Square to stop the clashes by cordoning and kettling the demonstrators.

"Military Police troops at the left. Army and police APCs [Armored Personnel Carriers] at the front. CSF [Central Security Forces] conscripts at the right. We're being besieged. #MOD," tweeted activist Jonathan Rashad.