"We believe (the attack) was carried out by an extreme Islamist group as a reprisal to the Christchurch mosque massacre in New Zealand", Mr Wijewardene said.
Ismail Ibrahim and other men trained at Wanathawilluwa played a role in attacks late a year ago to destroy Buddhist shrines and Church crosses, sources close to the investigation say.
The jihadist group claimed responsibility for the attacks earlier on Tuesday, some 48 hours after the near-simultaneous blasts tore through three high-end hotels popular with foreigners and three churches packed with Christians marking Easter.
The AFP photo caption says: "Sri Lankan mourners bury coffins for 61 victims killed in a bomb attack at Kebitogollewa in north-central Sri Lanka, 16 June 2006".
I don't know of any internal group in Sri Lanka that would have the capacity to pull off an attack like the one we saw on Sunday.
"A broader goal of this shadowy group may be to instill terror - just like al-Qaida and ISIS - the groups that NJT appears to model itself on", Kugelman told VOA.
"The preliminary investigations have revealed that what happened in Sri Lanka was in retaliation for the attack against Muslims in Christchurch", state minister of defence Ruwan Wijewardene told parliament.
Kugelman said the group's main activities in the past months have consisted of targeting Buddhist statues as the country's Buddhists feuded with Muslims.
NTJ has no history of large-scale attacks but came to prominence past year when it was blamed for damaging Buddhist statues.
Ardern's office said the prime minister had seen reports of the minister's statement.
Here is an AFP report on the suicide attacks in Sri Lanka on Easter Sunday, April 21, 2019 which have left more than 310 people dead.
Sri Lankan Health Minister Rajitha Senaratne said at a press conference Monday that all seven bombers wore explosive suicide vests. The posts are misleading; the image is actually a 2006 AFP photograph showing mourners after a bus hit a landmine killing dozens of people in northern Sri Lanka.
A Sri Lankan security official characterised NTJ as being a shell for ISIS and said it has been active in Kattankudy, an area in the eastern part of the country and home to one of its largest Muslim populations.
The death toll from the bombings has now climbed to over 300 people.
Security camera video shows a suspected suicide bomber with his backpack pausing to pat a child as he approached St. Sebastian church in Negombo.
A moment of silence was also observed at 08:30 on Tuesday, reflecting the time the first of six bombs detonated.
Flags were lowered to half-mast on government buildings, and liquor shops were ordered closed for the day.