Police say they have been looking for Nagori for a while
Police in the Indian state of Madhya Pradesh have arrested the leader of the banned militant group Students' Islamic Movement of India (Simi).
Safdar Nagori, general secretary of the organisation, was arrested in the city of Indore, police said.
Ten other Simi activists have also been arrested.
India says the organisation has links with Islamic militant groups. Simi was outlawed in 2001 and several of its senior members arrested.
The government has blamed Simi for blasts in Mumbai (Bombay) in 2003 in which at least 50 people were killed.
Simi has denied the allegation.
A senior police official in the city of Indore, Anil Kumar, told the BBC that the arrests were made on Wednesday night.
Police have described the arrests as "important".
They say Nagori is accused of carrying out unlawful activities against the country and he has been on their list of most wanted people for a while.