India's offer of help was conveyed by Modi during a telephone conversation with Indonesian President Joko Widodo.

"The Prime Minister offered deepest condolences on his behalf and on behalf of the people of India on the loss of precious lives in the earthquake and tsunami that hit Sulawesi region of Indonesia," the External Affairs Ministry said in a statement.

"The Prime Minister appreciated the resilience and courage of the people of Indonesia in facing the challenges emanating from the widespread devastation due to this grave natural calamity," it stated.

"In response to Indonesia's appeal for international aid, the Prime Minister offered to the President of Indonesia all possible assistance from India as a maritime neighbour and friend of Indonesia."

Mass graves were dug on Monday as Indonesia began burying hundreds of people killed by the earthquake and the tsunami that cracked streets, crumbled buildings and swept homes on the island of Sulawesi. At least 844 were confirmed dead and the toll was expected to climb, with heavily populated areas cut off from any assistance.

According to Monday's External Affairs Ministry statement, President Widodo thanked Modi for offer of assistance.

"The two leaders agreed that the details of India's relief assistance will be worked out through diplomatic and official channels," the statement said.