NEW DELHI - An Indian environmentalist and civil rights activist who campaigned against illegal mining has been shot dead by unknown assailants in the western city of Ahmedabad, police said Wednesday.

Amit Jethwa was campaigning against illegal mining in the Gir national park in the state of Gujarat and, according to the NDTV news channel, had recently filed public interest litigation against a senior local political figure.

"Two motorcyclists were waiting for him outside a building and when he came out they shot at him directly with a country-made rifle," joint commissioner of police Satish Sharma told AFP by telephone.

Jethwa, who was killed on Tuesday evening in central Ahmedabad, "had rubbed many people the wrong way" with his campaigns over illegal mining, Sharma said. The activist's father told NDTV that he was convinced political figures were involved in his son's murder.

Jethwa had recently filed a "right to information" request at Gujarat high court, making use of a civil liberties law introduced in 2005 that enables citizens to access information under the control of public authorities.

The law was intended to promote transparency and accountability in public institutions.

Illegal mining is rampant in India with the problem most acute in the states of Orissa, Karnataka and Jharkhand where private companies extract minerals without proper permits.

The practice often leads to encroachment on forests or other protected land and the contamination of local groundwater.