At least four people were killed in a series of blasts on Tuesday near a naval college in the eastern Pakistani city of Lahore, police said.

While officials have not identified the cause of the blasts, Pakistan is reeling from a bombing campaign waged by militants linked to al Qaeda and the Taliban.

Two blasts were heard near the Pakistan Navy War College, while another two blasts were heard elsewhere in the city minutes later, witnesses said.

It was not immediately clear if they were separate blasts or linked to an original explosion. Dawn TV said a suicide bomber had been responsible.

Interior Minister Hamid Nawaz told Reuters the blasts occurred inside the naval college, but he could not confirm the number of casualties or provide other details.

Police put the immediate death toll at four, while local TV stations said six had died.

Over 500 people have been killed in militant related violence since the start of this year.

Lahore, the capital of Punjab province, has rarely been targeted although a suicide bomber killed 19 people, mostly police, in an attack near the High Court in January.

PHOTO CAPTION

Map locating the eastern city of Lahore, Pakistan.