A teacher at a north Calcutta college was accused of giving rape threats to students on his Facebook page. Students gheraoed him outside campus on Saturday evening.

The students, most of them supporters of the SFI, asked him why he had made such posts.

Students said the teacher, a member of a teachers’ association owing allegiance to the Trinamool, would often target women, especially of the CPM.

Selim Box Mandal, vice-president of the Trinamool-led West Bengal College and University Teachers Association, said he had asked the teacher to desist from making offensive remarks against women and told him the association did not approve.

"We surrounded him around 4.45pm when he stepped out of campus. He apologised. We took him to Amherst Street police station. Police advised us to complain at Muchipara police station as the college falls under it," said a student. The students later lodged an FIR at Muchipara police station.

An officer said late on Saturday: "We questioned the teacher about the allegations."

Calls to the teacher went unanswered.