Sri Lankan officials have said the Islamist militant group National Thowheeth Jama’ath is responsible for Easter Sunday bombing attacks in the island nation that killed at least 290 people and injured 500 more.

Rajitha Senaratne, the country’s health minister, said the seven suicide bombers who carried out the attacks were Sri Lankan citizens affiliated with the domestic group, but that authorities suspect foreign ties as well. “There was an international network without which these attacks could not have succeeded,” Senaratne said in a news conference.

The group has not claimed responsibility for the bombings so far.

Here’s what to know about the suspected group behind the attacks.

National Thowheeth Jama’ath is a newly formed group

Very little is known about National Thowheeth Jama’ath, according to Alan Keenan, a senior Sri Lanka analyst with the International Crisis Group.

Prior to Sunday’s attacks, the group was mainly linked with the vandalization of Buddhist statues in Sri Lanka in December, he tells TIME. Until Monday, when the Sri Lankan government named the group, Keenan had never heard of it as an official organization.

Keenan says it’s possible the group splintered off from the political organization “Sri Lanka Thowheeth Jama’ath,” which carries hardline views and anti-Buddhist sentiments. Keenan also notes that many organizations in Sri Lanka use the name “Thowheeth Jama’ath,” making it difficult to pinpoint the origins of the group.

The name roughly translates to “a group in the name of oneness of God.”

The highly coordinated nature of the attacks, which targeted Roman Catholic churches in the midst of Easter celebrations, luxury hotels and a housing development, suggests that the group could not have carried out the bombings without outside assistance, Keenan says.

Sri Lankan officials received warning about the attacks and the group

Authorities in Sri Lanka had received warnings about the attacks about two weeks ago, Senaratne said at a news conference. Sir Lanka’s police chief Pujith Jayasundara sent an intelligence alert earlier this month saying National Thowheeth Jama’ath was planning attacks, AFP reports.

“A foreign intelligence agency has reported that the NTJ is planning to carry out suicide attacks targeting prominent churches as well as the Indian high commission in Colombo,” the alert read.

Sri Lankan police were on high alert for several days prior to the attacks, in fear that suicide bombers were targeting prominent churches, according to AFP.

Speaking to reporters, Senaratne said officials had received warnings but that the prime minister and others were “completely blind on the situation.” The New York Times reports that tensions over status between Sri Lanka’s Prime Minister Ranil Wickremesinghe and President Maithripala Sirisena were at least partly responsible for an error in communicating the warnings.

Wickremesinghe said Sunday that he and his cabinet had not received information about the warning, the Times reports.

“We must look into why adequate precautions were not taken,” he said.

The Times notes that a letter from a police official dated April 11 named National Thowheeth Jama’ath as the group believed to be planning the attacks, along with the names and addresses of some suspected members of the group.

Such attacks are unprecedented in Sri Lanka

Sri Lanka’s complex past does not include a history of violence between Christians and Muslims in the country, Keenan says.

“Sri Lanka is a very complicated place. Generally, there has been tension and violence between pretty much everybody,” he said. “But Muslims as a community have been the most restrained and non-confrontational at all. That’s why this does not fit with previous dynamics.”

About 70% of Sri Lankans are Buddhists, while 12.5% are Hindus. Muslims make up a little under 10% of the population, while about 7.5% are Christians. Predominantly Hindu Tamil insurgents fought for 26 years to establish independence from the government, dominated by the Sinhalese ethnic group, most of whom were Buddhists. The Tamil insurgents were defeated in 2009.

In recent years, violence in Sri Lanka has been propagated by Buddhist extremists, Keenan says. Hardline Buddhist groups, like Bodu Bala Sena, also known as Buddhist Power Force, has been accused of sowing hate and anti-Muslim violence.

Write to Mahita Gajanan at mahita.gajanan@time.com.