Eleven people were detained early on Friday in Karnataka's coastal city of Mangalore on suspicion of having links with terror groups, police said.
The Karnataka police, the state Anti-Naxal Force and Mumbai Police jointly raided several places in and around Mangalore, about 350 km from Bangalore, and picked up suspects for questioning.
Police sources said at least 11 people had been detained. However, AM Prasad, inspector general of police, said only four people had been held.
"Investigations are on. I cannot give any more details," Prasad told reporters in Mangalore.