India's elite counter-terror body National Investigation Agency (NIA) carried out searches at the houses of three suspects in Kerala on Sunday in connection with a suspected Islamic State (IS) module in which 21 Indians are said to have travelled to Syria and Afghanistan and joined the ISIS in 2016.

NIA sleuths searched the houses of two persons in Kasaragod district and one in Palakkad district of Kerala. These persons are suspected to have links with some of the accused people who exited India to join the "proscribed terrorist organisation ISIS/ Daish," the NIA said in a media statement uploaded on its website on Sunday.

"During the searches, a number of digital devices, including mobile phones, SIM cards, memory cards, pen drives, diaries with handwritten notes in Arabic and Malayalam, CDs with religious speeches, books of Dr Zakir Naik and Syed Kutheb have been seized from their residences," the statement said.

Mumbai-based TV evangelist Zakir Naik is on the run and is wanted by Indian security agencies.

The digital devices will be forensically examined and analysed and the three suspects are being questioned by NIA, the agency added.

The NIA is probing cases of disappearance of at least 21 people who had left Kerala under mysterious circumstances over a period of time and are suspected to have joined the ISIS. Among them, 17 are from Kasaragod and four from Palakkad and they include four women and three children, the statement said.

Indian media reports said some IS recruits from Kasargod and Palakkad had recently travelled to Sri Lanka where a string of Easter Sunday terror attacks targeting churches and five-star hotels left 253 people dead.

During a raid in Coimbatore town of Tamil Nadu state in December last year, the NIA reportedly found a video of Sri Lanka-based outfit National Towheeth Jamaath (NJT) founder Zahran Hashim who is one of the suicide bombers in the deadly Easter Sunday attacks in the island nation, said the reports.

According to Indian intelligence agencies, Hashim had travelled to Kerala and Tamil Nadu in the last two years.

During questioning of the three suspects held in Kasargod and Palakkad on Sunday, the NIA is understood to be trying to find out if there was any link between them and the suicide bombers behind Easter Sunday incidents in Sri Lanka.