Footage unearthed by Indian TV claims to shows the moment a suicide bomber walked into a Sri Lankan church before detonating a device.
The CCTV clip reportedly shows one of the attackers entering St Sebastian's Church in Negombo on Easter Sunday.
An estimated 290 people were killed in co-ordinated attacks.
The man can be seen walking into the church as worshippers congregated, casually stepping past people inside.
Moments later the bomb was detonated, Indian channel 9 TV - which broadcast the clip - reports.
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Sri Lanka today said it was invoking emergency powers in the aftermath of devastating bomb attacks on hotels and churches, blamed on militants with foreign links.
The emergency law, which gives police and the military extensive powers to detain and interrogate suspects without court orders, will go into effect at midnight on Monday, the president's office said.
Police said 87 bomb detonators were found at Colombo's main bus station, while an explosive went off near a church where scores were killed on Sunday when bomb squad officials were trying to defuse it.
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A night curfew will go into effect at 8pm, the government announced.
There was no claim of responsibility for the attack but suspicion was focusing on Islamist militants in the Buddhist-majority country.
Investigators said seven suicide bombers took part in the attacks while a government spokesman said an international network was involved.
Police had received a tip-off of a possible attack on churches by a little-known domestic Islamist group some 10 days ago, according to a document seen by Reuters.
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The intelligence report, dated April 11, said a foreign intelligence agency had warned authorities of possible attacks on churches by the leader of the group, the National Thawheed Jama'ut.
It was not immediately clear what action, if any, was taken on the tip-off.
Police said 24 people had been arrested, all of whom were Sri Lankan, but they gave no more details.
