[6] President of Sri Lanka Maithripala Sirisena banned National Thowheed Jamath on 27 April 2019 and designated it as a terrorist organisation along with Jammiyathul Millathu Ibrahim.

[4] The director of the International Center for the Study of Violent Extremism said that it "aims to spread the global jihadist movement to Sri Lanka and to create hatred, fear, and divisions in society.

[8][9][10] The NTJ was founded by Moulvi Zahran Hashim in the exclusively Muslim town of Kattankudy, which has been called a "fertile ground for extremism" and has seen Arabisation and the spread of Wahhabism since the 1980s with funding from gulf nations.

[10] The NTJ's leadership had been condemned by several Sri Lankan Muslim organisations in 2016 for advocating extreme fundamentalist indoctrination of children and for clashes with Buddhist monks.

During the 2015 General Election, however, he used the votes of his 2,000–3,000 followers to make Muslim politicians from both major and minor parties in the Eastern Province to sign an agreement which included a ban on music, gender segregation in seating arrangements, refusal to support "moderate" Muslims and Sufis as well as a condition saying the political parties should support groups such as the National Thawheed Jama'ath.

However the Attorney General's department did not take several letters by the Terrorism Investigation Division seriously and the CDs sent by the TID containing Zahran's lectures were given to lesser officials to watch by Senior State Counsel Malik Aziz who ordered them to compile a report.

The allegations included supply of empty shell casings to a factory owned by one of the bombers and Rishad's Moulvi advisor being arrested on suspicion of being a terrroist.

[23] K. D. N. Ranjith Asoka, Secretary Ministry of Industry & Commerce, rejected that Rishad requested any shell casings to be supplied to the bomber's factory.

[27] Zahran was a radical Islamist imam believed to be the mastermind behind the Sri Lanka bombings, preached on a pro-ISIL Facebook account, known as "Al-Ghuraba" media, and on YouTube.

The report read that "the NTJ is planning to carry out suicide attacks targeting prominent churches as well as the Indian high commission in Colombo.

Security forces discovered detonators, firearms, ammunition, ammonia packets and other explosives including C4, incendiary bombs, knives, GPS, military camouflage, katana swords, machettes and suicide jackets from various parts of the country.

[38][39][40][41] On 5 May, government forces discovered a 15-acre land in Kattankudy disguised as a farm and is believed to be a training camp for militants and the next day raided a two-story guesthouse in Nuwara Eliya based on intel by arrested suspects.

[1][50] The NTJ is believed to have received funding from foreign entities to build its mosques and General Secretary of the SLFP, Dayasiri Jayasekara speaking to the media claimed that there was "firm evidence" to prove that religious extremists in Saudi Arabia and Qatar have been funding Islamic extremists in Sri Lanka and requested the Saudi and Qatari government to take action against these groups.