(Image source from: The Telegraph)

Days after deadly blasts in Sri Lanka, the CCTV footage showing one of the alleged suicide bombers entering St Sebastian Church in Negombo, moments before a blast ripped through the church during the Easter Sunday mass was released by Sri Lankan channel on Tuesday.

The video shows the suspect wearing a backpack, walking towards the church with people walking around him. A man and a girl holding hands were seen crossing paths with the alleged suspect who pauses to pat the girl before he continues to walk towards the church.

#WATCH Colombo: CCTV footage of suspected suicide bomber (carrying a backpack) walking into St Sebastian church on Easter Sunday. #SriLankaBombings (Video courtesy- Siyatha TV) pic.twitter.com/YAe089D72h

— ANI (@ANI) April 23, 2019

An eyewitness, Dilip Fernando, who left the St Sebastian's church right before the blast, claimed to have seen the young man carrying a hefty bag, get into the church at the end of the mass. "He touched my granddaughter's head on the way past. It was the bomber," he was quoted as saying by news agency AFP.

The family wondered why he was entering the church with a mass nearly over, Fernando said, adding that the man had looked to be around 30 and "very young and innocent", according to his relatives.

"He was not excited or afraid. He was so calm," he told AFP. Shortly after the man entered the church, there was a massive blast.​

In the CCTV footage, the man is seen entering from the front door of the church through the dozens of people seen offering prayers. He is dressed in a light-blue shirt and black pants.

The Islamic State group on Tuesday claimed a series of bombings that killed more than 320 people in Sri Lanka and released a photo and video of the men it said were responsible.

"Those that carried out the attack that targeted members of the U.S.-led coalition and Christians in Sri Lanka the day before yesterday is Islamic State group fighters," IS propaganda agency Amaq said in a statement. In a later statement, the group gave the noms de guerre of seven people it said were behind the "blessed attack" that targeted Christians during their "blasphemous holiday".

Amaq also released a photo of eight men it said were behind the blasts. Seven of them had their faces covered and three of them held knives. The one man who displayed his bearded face also appeared to be carrying an assault firearm.

Amaq later released a video of the eight fighters pledging commitment to IS supremo Abu Bakr al-Baghdadi in Arabic, a black IS flag hanging in the background.

The bombings on Sunday targeting churches and high-end hotels are among the deadliest such attacks worldwide since the 2001 strikes on the United States.

The Sri Lankan government on Tuesday blamed National Thowheeth Jama'ath (NTJ) Islamist group for the blasts, saying they were carried out in retaliation for last month's attacks on two mosques in New Zealand.

The presidency cited intelligence saying "international terror groups" were backing Sri Lankan extremists.

Police sources told AFP Tuesday that two Muslim brothers - sons of a wealthy Colombo spice trader - were among the perpetrators of the attacks.

They blew themselves up as guests queued for breakfast at the Shangri-La and Cinnamon Grand hotels in the capital, the source said.

The pair were key members of the NTJ, which the government has previously blamed for defacing Buddhist statues, according to an investigation officer.

The IS statement on Tuesday said three fighters it named as Abu Obeidah, Abu Baraa, and Abu Moukhtar were behind the attacks on the Shangri-La, Cinnamon Grand and Kingsbury hotels.

Three other fighters it named as Abu Hamza, Abu Khalil and Abu Mohammad carried out attacks on churches in the cities of Colombo, Negombo, and Batticaloa, it said.

The seventh fighter, Abu Abdallah, killed three police officers in an attack in a Colombo suburb, it said.

By Sowmya Sangam