The Indian Union Muslim League on Sunday came out in support of preacher Zakir Naik, saying the "advocate of peace theory in Islam" is being harassed for no "valid reason".

Addressing a press conference in Kozhikode, IUML MP and former minister E T Mohammed Basheer said, "Naik is an advocate of peace theory in Islam. The action by the authorities against the Islamic preacher is a violation of the freedom of expression. He is being harassed for no valid reason."

"The probe against Naik is being carried out in a prejudiced manner," Basheer alleged and demanded that authorities stop harassing the preacher.

"Since the launch of Islamic Research Foundation in 1991, Naik has travelled to many parts of the world and delivered a large number of speeches and organised several debates. In view of these facts, he should not be harassed," he said.

Basheer alleged that the Maharashtra government has launched an investigation in a "prejudiced manner" intending to oppose his activities and portray him in a "wrong way".

"Those who believe in the Indian Constitution which guarantees freedom of expression should come forward to oppose the move," he said.

A video footage of a speech by Naik in which he speaks against Islamic State, was also played during the press conference.

Naik has come under the scanner over reports that one of the Dhaka attackers was allegedly inspired by his speeches.