Two sons of a wealthy spice trader carried out suicide blasts in the Sri Lanka terror attacks on Easter Sunday, it has been claimed.

The Muslim brothers, Ilham Ibrahim and Inshaf , blew themselves up as guests queued for breakfast at the Shangri-La and Cinnamon Grand hotels in the capital.

They were in their late twenties and operated their own 'family cell', an investigation officer said as Sri Lankan police continue to probe the bombings that killed 321 people. It is not known where their parents are.

ISIS have released an image of the suspected suicide bombers. It is unclear which two in the group are the brothers. Pictured centre is purported National Thowfeek Jamaath leader Moulvi Zahran Hashim

The Muslim brothers blew themselves up as guests queued for breakfast at the Shangri-La (pictured) and Cinnamon Grand hotels in the capital

They were in their late twenties and operated their own 'family cell', an investigation officer said. It is not known where their parents are. Pictured: Shangri-La Hotel

When the Special Task Force went to the house to investigate, one brother's wife set off a bomb, killing herself and her two children. Pictured: soldiers patrolling near luxury hotels today

One brother gave false identity details when he checked into the hotel, but the other gave a real address which led police commandos to their family home in a commercial area of Colombo.

When the Special Task Force went to the house to investigate, Ilham Ibrahim's wife, Fatima, set off a bomb, killing herself and her two children, according to police sources.

Three police commandos were killed in the blast, and several extended family members are among those in detention.

'It was a single terror cell operated by one family,' the investigator said. 'They had the cash and the motivation. They operated the cell and it is believed they influenced their extended family.'

Pictures which appear to show the suspected suicide bombers, including purported National Thowfeek Jamaath leader Moulvi Zahran Hashim, pictured, pledging allegiance to ISIS are being circulated by ISIS fanatics

'What we have gathered so far is that they had indicated to their close family what they were going to do,' another senior police officer said.

'It looks like they were inspired by foreign terrorist groups, but to what extent they had direct links is still unclear.'

The brothers had been involved in their father, Yoonus Ibrahim's lucrative Colombo spice export business, investigators said.

A focus of the inquiry will be to find out whether there was a foreign influence in their radicalisation and how the children of such a wealthy family had become involved, an official source said.

The pair were key members of the Islamist National Thowheeth Jama'ath (NTJ) group, the official added.

Burials for the dead began today in Negombo, pictured. The attacks have sparked local and international outrage, and have been condemned by Sri Lankan Muslim groups

Relatives mourning beside the coffin of one of the suicide bomb victims at St Sebastian's Church in Negombo

ISIS has claimed responsibility for the attacks, but the government has blamed the NTJ.

A minister said Tuesday the bombers may have struck in revenge for attacks on two New Zealand mosques last month which left 50 dead.

Investigators said it was not known whether the brothers were in contact with the other bombers.

The first wave of attacks struck during busy Easter services at churches in the cities of Colombo, Negombo and Batticaloa.

More bombs ripped through three luxury hotels in the capital city of Colombo: the Kingsbury, the Shangri La, and the Cinnamon Grand.

The group also planned another attack at a fourth hotel, but the suicide bomber either failed to detonate his device or decided against doing so, official sources said.

Wreckage: Sri Lankan security personnel inspect the damage at St Anthony's Shrine following the Easter Sunday bombing

A view of St. Sebastian's Church, which was damaged in the blast in Negombo, north of Colombo, on Sunday morning

Sri Lankan soldiers secure the area around St. Anthony's Shrine after a blast in Colombo on Easter Sunday

After the Shangri-la blast, staff at the unnamed hotel the would-be attacker checked into became suspicious and reported him to police.

The man was tracked to a lodging near the capital, where he blew himself up when confronted by police, killing two bystanders.

'What we have seen from the CCTV footage is that all the suicide bombers were carrying very heavy backpacks. These appear to be crude devices made locally,' the source said.

Police are also currently on the hunt for a van and a lorry that are believed to be carrying explosives, reports News 1st. They are also on the look out for three motorbikes, a cab and a van.

With 321 people confirmed dead, including at least 39 foreign nationals, and over 500 wounded, Sri Lanka has declared a state of emergency and launched a desperate hunt to head off more attacks.

Forty people were under arrest on Tuesday over the suicide bomb attacks - the worst atrocity since Sri Lanka's civil war ended a decade ago.

The whereabouts of the NTJ leader, Zahran Hashmi, is unknown.

He was linked to the vandalising of Buddha statues on December 26 at the central town of Mawanella.

The local Muslim community had been complaining to authorities about Hashmi since 2017.

Residents of the village in the east of the country where he lived had demanded police action against him over his radical comments and acts, community leaders revealed

'He was a threat to moderate Muslims in the east and we had made several complaints,' one Muslim leader told AFP.

The NTJ were the subject of an intelligence warning ten days before the devastating blasts but this was not passed to top ministers.

A separate investigation is underway into why more was not done to stop the brothers and the other attackers.