New Delhi  - Indian Prime Minister Manmohan Singh will undergo heart surgery over the weekend and was likely to be admitted to a New Delhi hospital later on Friday, media reports said.

Singh, 76, underwent a coronary angiography as part of a series of heart-related tests at the All India Institute of Medical Sciences (AIIMS) on Tuesday and Wednesday and was discharged on Thursday.

The medical tests revealed multiple arterial blockages and doctors were preparing for a surgery as early as Saturday, the NDTV network reported.

It was not clear whether Singh will undergo a bypass surgery or angioplasty, the report said, adding he would be taken to AIIMS later on Friday.

India's External Affairs Minister Pranab Mukherjee, the most senior member of the United Progressive Alliance government after Singh, will take charge in the absence of the prime minister.

Citing medical sources, the CNN-IBN news channel reported that Singh will have to rest after the procedure and will be able to resume work only by March.

India is scheduled to hold general elections before May.

There were concerns over the septuagenarian leader's health after he complained of chest pain this week, but doctors had said that he was not "in any danger."

Singh underwent a bypass surgery in Britain in 1990 and had an angioplasty in 2004. The Indian prime minister is a diabetic and works for nearly 18 hours a day. (dpa)