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At least 58 cadets and guards have been killed after militants attacked a police college in the Pakistani city of Quetta, officials say, the BBC reports.

Three militants wearing suicide bomb vests entered the college late on Monday, reportedly taking hostages.

A major security operation lasted for hours and all attackers were killed.

No group has said it carried out the assault, but Quetta has seen similar attacks by separatists and Islamist militants in recent years.

Hundreds of trainees were evacuated from Balochistan Police College as troops arrived to repel the militants. Local media reported at least three explosions at the scene.

The police academy is home to hundreds of students and many of the cadets who died were killed in the blasts, said Major General Sher Afgan of the Frontier Corps.