A group of al-Qaida prisoners was caught trying to tunnel out of Iraq's Abu Ghraib prison, an official said on Sunday, after the militants said they would step up their fight against the government.

Iraq's Shiite-led government is concerned that Sunni Muslim militants will get a boost from the insurgency in neighboring Syria, where mainly Sunni rebels are battling President Bashar al-Assad.

Jail breaks are common in Iraq and security at prisons was beefed up this week after five militants stormed a police counterterrorism headquarters on Tuesday in an attempt to free al-Qaida prisoners. All five were killed in a long gun battle.