This is a breaking news story and will likely be updated...

At least 230 people were killed and over 100 injured after gunmen opened fire on worshipers at a Sufi mosque in Egypt's Sinai Peninsula during Friday prayers. 

The attackers also detonated explosives that were planted inside the mosque, located just over 100 miles northeast of the Egyptian capital.

As the New York Times reported:

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The attackers traveled in four-wheel-drive vehicles and exploded bombs inside the mosque in Bir al-Abd...then sprayed worshipers with gunfire as they fled, state media reported. A military official said that a suicide bomber was involved in the attack.

The attackers lingered at the scene even as emergency workers arrived to treat the injured, and opened fire on several ambulances, Ahmed el-Ansari, a senior government health official, told state television.

There was no immediate claim of responsibility for the attack, which was described as the deadliest to strike in the Sinai region in years. 

Three days of mourning have been declared, according to Egyptian state media.