Gunmen shot dead a man once charged with the 2013 killing of an Indian national jailed in Pakistan for alleged spying, according to officials and a police report, against a backdrop of fraught relations between the rival South Asian powers.

Ties have been on ice since a suicide bomb attack on an Indian military convoy in Kashmir in 2019 that India traced to Pakistan-based militants. India responded with an airstrike on what New Delhi said was a militant training camp in Pakistan. Islamabad said the target was a seminary only.

The convicted spy, Sarabjit Singh, died in hospital in 2013 after having been attacked with bricks and blades by two fellow inmates in a Pakistani jail.

Two police officials, speaking on condition of anonymity, told Reuters on Monday that one of Singh's suspected attackers in 2013 had been identified as former inmate Amir Sarfraz Tamba, and the police record seen by Reuters said the same.

However, a Pakistani court acquitted Tamba of involvement in the murder in 2018.

In Sunday's incident, according to a police report, his brother Junaid Sarfraz told police the gunmen barged into Tamba's home in a Lahore neighbourhood and killed him with three gunshots.

"We suspect India's involvement in this, but will wait for the investigation to be completed," Interior Minister Mohsin Naqvi told a news conference.

He said the killing echoed a pattern of certain targeted attacks in recent months that Islamabad had blamed on New Delhi.

The foreign ministries of the two South Asian powers did not respond to a Reuters request for a comment. Reuters tried to contact Sarfraz but his mobile phone was constantly switched off.

Earlier this year, Islamabad said it had credible evidence linking Indian agents to the killing of two of its citizens on its soil, which New Delhi branded as an attempt to peddle "false and malicious anti-India propaganda".

Last year, Canada and the United States separately accused Indian agents of links to assassination attempts on their soil.

India has denied the Canadian accusations and launched an investigation into the U.S. allegations.

Islamabad says the alleged Indian network of "extra-judicial and extra-territorial killings" has become a global phenomenon.

New Delhi also accuses Islamabad of training and harbouring Islamist militants responsible for attacks in its part of the disputed Himalayan region of Kashmir, divided between the two nations.

They have fought three wars since independence from Britain in 1947.

(Writing by Asif Shahzad; editing by Clarence Fernandez and Mark Heinrich)