Former Prime Minister Dr Manmohan Singh has been admitted to Delhi's All India Institute of Medical Science (AIIMS) after he complained of chest pain, sources said.

He is under the supervision of Dr Nitish Nayak. Singh is kept under observation at the Intensive Care Unit (ICU).

In 2009, Singh underwent a successful coronary by-pass surgery at AIIMS, a complex beating-heart operation that took nearly 14 hours.