One nation spreading terror in South Asia, PM Modi at G20 summit
He also appealed the grouping to "isolate and sanction supporters of terrorism".
At the two-day G20 summit which began in the eastern Chinese city of Hangzhou, India raised the issue of terrorism at various sessions.
Modi told Chinese President XI Jinping how the scourge of terrorism was affecting the region.
"There are some nations that use it as an instrument of state policy. One single nation in South Asia is spreading agents of terror in our region," Modi said, without naming Pakistan.
India's ties with Pakistan have soured after Islamabad declared Jammu and Kashmir terrorist Burhan Wani, shot dead by security forces, as a "martyr".
"For us a terrorist is a terrorist," Modi said. He was speaking during his intervention at the last session of the G20.
The Prime Minister said "growing forces of violence and terror pose a fundamental challenge" and urged the international community to act in unity and respond against terrorism.
"India has a policy of zero tolerance to terrorism. Because anything less than that is not enough," he said.
In his meeting with President Xi, Modi expressed concern over terrorism emanating from Pakistan's restive regions of Giligit-Baltistan and Pakistani Kashmir where the China Pakistan Economic Corridor is coming up.