India on Saturday strongly condemned the assassination of Sri Lankan foreign minister Lakshman Kadirgamar, describing it as a 'heinous act' of terrorism by those seeking to undermine the island nation's unity and political stability.

"We have learnt with deep shock and profound grief of the brutal assassination of Sri Lanka's distinguished foreign minister and long-standing friend of India," External Affairs Ministry spokesman Navtej Sarna told reporters in New Delhi.

"This has been a heinous act and we condemn it unreservedly," he said.

Sarna said India was confident that the government and people of Sri Lanka would rise to the challenge and 'defeat the forces which seek to undermine Sri Lanka's unity and political stabiliy.'

Also read: Emergency imposed in Sri Lanka

He hoped the perpetrators of this terrorist act would be brought to justice.

Maintaining that India's support for unity and territorial integrity of Sri Lanka remained 'constant and undiluted,' the spokesman said New Delhi would always extend its full support to the friendly neighbour in its hour of need.

He conveyed the sincere condolences of the government and people of India to Kadirgamar's wife and the rest of the family on their irreparable loss.

"Our prayers are with them in their moment of sorrow," he said.