Mr Singh is likely to be in hospital for at least a week after surgery
Indian Prime Minister Manmohan Singh is "conscious and stable" after undergoing successful heart bypass surgery in Delhi, his team of doctors said.
During the 11-hour operation, surgeons performed five bypasses on the 76-year-old leader.
He is expected to remain in hospital for seven to eight days and should be "fully functional" in six weeks.
The ruling Congress Party says he will still lead the party in the forthcoming general election which is due by May.
"The entire country is rejoicing because our prime minister has come out successfully from the operation," Congress spokesman Veerappa Moily was quoted by AFP as saying.
Mr Singh, who previously had bypass surgery in 1990 and an angioplasty in 2004, had complained of chest pains earlier in the week.
He was admitted to hospital on Friday. The operation began at 0845 local time (0315 GMT) on Saturday and ended at 1930 (1400 GMT), his personal physician said.
The operation was performed at the All India Institute of Medical Sciences, India's top state-run hospital, by an 11-member team of doctors.
According to the BBC's Jill McGivering, this is not a good time for the prime minister to be removed from the political fray, given tense relations with Pakistan in the wake of the Mumbai attacks.
Mr Singh's physician Dr KS Reddy (right) says he is "very, very stable"
Congress has so far dismissed concerns that Mr Singh's health would interfere with its current election campaign.
But there has been widespread speculation that party chief Sonia Gandhi has been lining up her son, Rahul Gandhi, heir to India's powerful Gandhi dynasty, as the country's next prime minister.
Mr Singh has largely been in good health since he was sworn in as prime minister in May 2004, but he recently underwent prostate surgery and has also had cataract treatment.
Mr Singh, who studied economics at Cambridge and Oxford, became India's finance minister in 1991 when the country was plunging towards bankruptcy, and is widely regarded as the architect of the country's economic reform programme.
The quietly spoken economist-politician is also seen as the cleanest politician in India, a subject dear to voters' hearts.
Government officials said that Foreign Minister Pranab Mukherjee will take charge of cabinet meetings during the prime minister's absence.