The Indian government has provoked outrage by directing universities not to invite foreign scholars to conferences of a "political, semi-political, communal or religious nature" without getting security clearance from the home ministry.
University teachers' bodies said the move was an attack on academic freedom that represented the "Talibanisation" of academia.
Invitations to scholars from Pakistan, China, Sri Lanka and Bangladesh will need clearance from the foreign office and the home ministry, regardless of the subject of the conference.
Invitations to Indian scholars from universities and academic institutions abroad will also need ministry permission.
"Secret" guidelines advise universities to avoid inviting foreign scholars to speak on "human rights or sensitive technical subjects that can be utilised as a platform for any particular line of propaganda".
Institutions have been asked to submit all such proposals to the home ministry six weeks before the conference for clearance.
The government defended the guidelines. It said they were intended to prevent a situation that might cause "embarrassment to the government or to friendly countries".
But Kamal Mitra Chenoy of New Delhi's Jawaharlal Nehru University said they were part of the rightwing BJP-led government's agenda to stifle freedom of expression. "It is part of a pattern that is absurd and dangerous," he said.