CAIRO — At least 235 people were killed when gunmen opened fire and bombed a mosque in Egypt's volatile Sinai Peninsula on Friday. Government officials said 109 more had been injured in the attack — among the deadliest in Egypt's history.

Images from inside the building showed dozens of bodies wrapped in blood-soaked cloth lined up on the carpeted floor.

Police sources told the Associated Press that men in four off-road vehicles opened fire on worshippers in the al-Rawdah mosque in the town of Bir al-Abd, which is about 25 miles from the North Sinai provincial capital of el-Arish. NBC News could not immediately independently verify that account.

Two eyewitnesses and a security source told Reuters that the suspected militants targeted supporters of the security forces attending prayers. Citing official sources, state-run MENA reported that the mosque is largely attended by Sufi Muslims — a form of Islam considered heretical by some conservatives and extremists like the Islamic State group.

Around 50 ambulances were transferring victims to hospitals, according to the Ministry of Health. A statement issued by Egypt's General Prosecutor Nabil Sadiq put the death toll at 235, with at least 109 others wounded.

There have been a wave of attacks on the country's Coptic Christian minority, but strikes on mosques are rare and have shocked many throughout Egypt.

A Health Ministry official told Al Jazeera TV that “there were many people inside the mosque — it’s only a small mosque."

Gunmen shot worshippers fleeing the initial attack, he added.

While Egypt's security forces have been battling an Islamist militants in northern Sinai for years, violence picked up after the 2013 ouster of President Mohammed Morsi. A new group called Ansar al-Islam claimed responsibility for a bloody October attack on Egyptian police.

The conflict has killed hundreds of soldiers and militants over the years, although journalists are banned from the area and exact numbers are unclear.

President Abdel-Fattah el-Sissi declared three days of mourning and called a meeting of security officials after the attack.

This is a developing story, please check back for updates.

Charlene Gubash reported from Cairo. F. Brinley Bruton reported from London.