NEW DELHI - INDIA'S Prime Minister was recovering yesterday after a complicated heart operation that has raised speculation about a possible successor three months before a general election.

Dr Manmohan Singh was in a stable condition at All India Institute of Medical Sciences (Aiims) after a heart bypass operation that lasted eight hours.

Shortly after, Congress party spokesman Veerappa Moily told reporters: 'The entire country can rejoice. He will come back rejuvenated.'

But while the news sent a wave of relief throughout India, the 76-year-old is expected to be out of action for weeks, and what will happen in the run-up to the election remains unclear.

For now, External Affairs Minister Pranab Mukherjee, the most senior minister, will head the Cabinet Committee on Political Affairs, in effect running the government in Dr Singh's absence.

Defence Minister A. K. Antony will stand in for him at ceremonial functions, including tomorrow's Republic Day celebration.

Because it was repeat surgery, doctors had to work painstakingly on the tissue beneath the breast bone before entering the heart, according to experts familiar with the procedure.

Dr Singh underwent his first bypass operation in Britain in 1990 and an angioplasty in 2003.

This time, he was driven to Aiims on Friday night, hours after lunching with his wife and two daughters at home. A third daughter lives in the United States.

Unlike typical bypass operations, instead of moving Dr Singh to a heart-lung machine, his heart was kept beating during the process, while surgeons repaired the organ. It was the first time this procedure had been done at Aiims, India's premier medical research hospital.

Meanwhile, his poor health has renewed speculation about his successor.

Congress president Sonia Gandhi has said Dr Singh will lead the campaign for the national elections, which have to be held by May.

However, it will be at least a month before he is able to take the full pressure of his job and a full recovery may take up to two months.

While former prime minister Atal Bihari Vajpayee had a deputy prime minister , the Congress-led United Progressive Alliance has been reluctant to name one for Dr Singh.

As well as running the government in the meantime, Mr Mukherjee will present the annual budget on Feb 12, as Dr Singh has been Acting Finance Minister since November.

Mr Mukherjee is by far India's most experienced minister, but an episode dating to Indira Gandhi's assassination in 1984 has been used by critics to paint him as a man of excess ambition.

Asked who should step in for the slain premier, Mr Mukherjee is said to have responded that it should go to the most senior member of Cabinet - himself.

In that event, the Congress party pitchforked Mr Rajiv Gandhi into the job.

But this time, he remains one of the main candidates to eventually succeed Dr Singh, with Mr Rahul Gandhi, heir to one of India's most powerful family dynasties, also emerging as a heavyweight contender.

velloor@sph.com.sg