Jehovah's Witnesses in the Kalamassery area of Kerala's Kochi on Sunday morning, police said, reported agencies.
Kalamassery CI Vibin Das said the first explosion took place around 9 am and multiple blasts followed thereafter, over the next one hour.
The three-day meeting, which commenced on October 27, concluded on Sunday.
According to officials, more than 2,000 people were attending the prayer meeting when the blasts took place.
The incident occurred one day after Khaled Mashal, the former leader of the Hamas militant group, delivered a virtual address at a pro-Palestine protest during the Israeli military offensive in Gaza.
Reacting to the participation of the Hamas leader in the protest on Saturday, Israel's ambassador to India, Naor Gilon, posted from his X handle, «Mashal calls participants to: Take the streets and show anger, prepare for jihad (against Israel), support Hamas financially, promote Palestinian narrative on social media, it's time to add #HamasISIS to #India's terror list.»
Further details are awaited.
(With inputs from ANI)