Kashmiri separatist leader Syed Ali Shah Geelani is undergoing surgery at the Tata super speciality hospital for kidney cancer on Monday.

He has been ailing for the past few years and has undergone treatment in New Delhi for various ailments.

Geelani's doctor Dr Samir Kaul had suggested that Geelani should receive further treatment in the US. Acting on this recommendation, the Indian government -- at the intervention of Prime Minister Manmohan Singh -- issued him a passport to enable him to travel.

However, Geelani is still waiting for his visa to be issued. In the meantime, Geelani, who needed immediate medical attention, was admitted to a New Delhi hospital.