Over 250 people were killed in a string of bombings in Sri Lanka on April 21. (File)

Indian intelligence agencies are conducting background checks on all Sri Lankan nationals and tourists who visited India in the last four months. Special focus is being paid to ones who visited Kashmir.

The exercise comes amid reports that the Sri Lankan army chief has claimed that terrorists who carried out attacks in Colombo visited India - Kerala, Kashmir and Bengaluru for training and also establishing links with terror groups operating in these areas.

"We are trying to verify the assertion being made by Sri Lankan agencies. As of now nothing has been shared with Indian government. But we are doing our background checks," a senior government functionary told NDTV on the condition of anonymity.

According to him, Kashmir is always on the radar for terror groups that want to expand their base and that is why special focus is being paid to the region while doing checks.

As per the Home Ministry, as many as 15,000 foreign tourists have visited Kashmir this year in the first four months. "Most of them are Malaysians followed by [those from] Thailand," said a senior official.

According to him, only 20 Sri Lankans visited the valley during this period. "We are doing background checks on them. But these are registered tourists," he added.

Sources indicate if these attackers would have visited Kashmir for training, they would have travelled with some local contact. "There would be no record in this case but we are still trying to get information," the official said.

Intelligence agencies are worried about the implications of Sri Lanka blasts in India as it hints at active ISIS ideology. "Even though ISIS has been disseminated in Syria and Iraq but there are still takers of its worldview. There are youngsters who are still being radicalised," he stated.

In 2010, as many as five young men from Kerala were identified for having links with the Pakistani terrorist group Lashkar-e-Taiba. Officers recall subsequently they were killed in North Kashmir.

According to the Research and Analysis Wing (R&AW), as many as 130 Indians have traveled to Syria and have been identified for having links with ISIS. And about same number who have been brought back or have been booked in various cases. "As far India is concerned, all affiliated with ISIS are accounted for," said a senior level officer.

However, agencies are alert as they feel that even if a miniscule fraction of the population is being radicalised, the damages caused by them can be exhaustive. 'It's a wakeup call. We can't be complacent anymore. The threat has come knocking very close to our home it is very serious," a senior functionary in government said.

Sri Lanka has been on edge since the Easter attacks that killed 257 people and wounded nearly 500 others on April 21.