Former Indian prime minister Atal Bihari Vajpayee was admitted to hospital late Tuesday suffering from a chest infection, reports said.
The 84-year-old was brought to the All India Institute of Medical Sciences in New Delhi Tuesday night after he developed a temperature, the Press Trust of India news agency said.
Hospital medical superintendent D.K. Sharma said Vajpayee was in a stable condition, PTI reported.
Vajpayee stepped down as prime minister in May 2004 after his Hindu nationalist Bhartiya Janata Party suffered a stunning defeat at the hands of the Congress party in national elections. The following year he announced his retirement from active politics.
BJP leader Vijay Goel said doctors did not think that the former premier's condition was serious, PTI reported.
Due to ill health, Vajpayee has been making fewer public appearances in the last couple of years, the agency said.
Vajpayee's last tenure as prime minister from 1999 to 2004 was one of the most eventful in the country's history during which India conducted nuclear tests, made strides towards peace with Pakistan and achieved major economic progress.
He held office twice briefly before that, once for 13 days in 1996 and also for one year in 1998.
A bachelor and former journalist, Vajpayee was a founding member in 1951 of the right-wing BJS (Indian People's Society), the BJP's predecessor.
BJS president for a decade until 1973, he was jailed in 1975 along with thousands of political activists when then Congress prime minister Indira Gandhi imposed emergency rule in India. He was freed two years later.
A skilled orator in Hindi, Vajpayee said, after stepping down as prime minister, that he would love to resume writing poems.