Singh is due to lead the ruling Congress party into general elections in May, but fears over his health could undermine a re-election campaign.

The prime minister has had a history of heart problems.

Singh underwent bypass surgery in 1990 in the UK, and had an angioplasty in 2003.

Officials said he also underwent wrist surgery in 2006, prostate-gland surgery and a cataract-removal procedure last year.

Deepak Sandhu, Singh's spokeswoman, said he will undergo "coronary artery bypass graft surgery", performed by a team of doctors.

The doctors come from the All India Institute of Medical Sciences - the county's premier state-run hospital - and the Asian Heart Institute in Mumbai, she said.