Manohar Parrikar (Photo by SAM PANTHAKY/AFP/Getty Images)

India’s former defence minister Manohar Parrikar, a close aide of Prime Minister Narendra Modi, passed away on Sunday at the age of 63.

Parrikar had undergone months of treatment for pancreatic cancer before his death, Indian officials said.

Modi described him a “true patriot and exceptional administrator”.

“His impeccable service to the nation will be remembered by generations,” Modi wrote on Twitter.

The government announced a day of mourning on Monday and called for the national flag to be flown at half-mast.

Parrikar was India’s defence minister in September 2016 when New Delhi said it sent special commandoes across the Kashmir border into Pakistan to destroy militant facilities, in response to an attack on one its army bases that killed 19 soldiers.

Islamabad denied that India had carried out the so-called “surgical strikes”.

Parrikar stepped down as defence minister in 2017 to lead his home state of Goa. It was his fourth term as chief minister of the western coastal state.