Sri Lankan authorities banned National Thawheed Ja’amath (NTJ), the Islamist group believed to have orchestrated the Easter Sunday jihadist attacks against Christians this month, and arrested its leader a week after the bombings.

President Maithripala Sirisena also announced a ban on all face coverings in public, including the niqab and burqa, Islamic garments typically worn by fundamentalist Muslims. Hijab, the hair covering that leaves the face exposed, is more typical among moderate Muslims and not affected by the ban.

Sirisena personally ordered the ban on NTJ on Saturday in the interest of public safety. The ban prevents the group from lawfully assembling or fundraising and freezes its assets.

Following the order, police raided the mosque in Kattankudy that served as the headquarters of NTJ, shutting it down and detaining the head of the group in the Colombo area. Identified in Sri Lankan media alternatively as “Farook Mohammed Tawas” and “Mohammad Farook Mohammad Fawaz,” police received permission to detain and question the leader for at least 72 hours for any information that may reveal a jihadist plot and prevent another massacre. Sri Lanka’s News 1st reported on Monday that police found Fawaz in possession of NTJ propaganda and a cellular phone full of “videos related to the eight Easter suicide attacks” and photos of the cars the suicide bombers used to reach their targets.

Suicide bombers successfully executed attacks on three churches and three hotels on Easter Sunday, targeting Christians observing the holiday with Mass and breakfast. Authorities estimate that at over 250 people were killed in the attacks, many children. Witnesses say the bombers appeared to target children by detonating their weapons in the back of the churches, were parents typically hover in case they have to tend to their young children and leave with minimal disturbance to other worshippers.

Shortly following the attack, police identified NTJ, a previously little-known group that had focused on defacing Buddhist statues, as the responsible party. The Islamic State then responded by claiming the attack for themselves and publishing video and photos of the people they alleged planned and committed the attack. Sri Lankan police identified the only person in the video with their face uncovered by a mask or veil as imam Mohammed Zahran Hashim, the head of NTJ. Hashim is believed to have planned the attack and recruited the suicide bombers responsible.

Sri Lanka’s Daily Mirror published an interview last week with a man claiming to be the head of NTJ, identified as Moulavi Thawufeek, who told the newspaper that the group had disassociated from Hashim when he began to deliver radical sermons at their mosque and immediately notified the police in 2012. Locals in Kattankudy insisted that the claim that NTJ had ostracized Hashim was “a complete lie” and that he had visited their mosque six weeks before the attacks. Hashim spent years posting his violent sermons on social media like Youtube and Facebook, where he attracted thousands of followers.

Beyond the NTJ mosque, the Mirror revealed that 11 mosques in Kattankudy preached Islamic fundamentalism. Eight of them the newspaper identified as “fundamentalist” and another three as “Wahhabist,” referring to a specific fundamentalist strain of Islam native to Saudi Arabia. Elsewhere in the country, former President Chandrika Bandaranaike Kumaratunga complained this weekend that the Sri Lankan government has reason to be aware of the presence of radical Islamist madrassas, or schools, serving Sri Lankan children nationwide, but have done nothing to shut them down.

Police in the island nation alerted citizens Monday that they have reason to believe jihadist outfits are planning more attacks. Local outlets reported that police arrested 150 people in connection with the Easter terrorist attacks and questioned another 100 nationwide. Raids across the country have revealed hidden stashes of weapons in mosques around Colombo. On Monday, police raided a three-story house that appeared to be in use as a jihadists bunker, local media reported, without specifying what authorities found inside.

Sri Lankan authorities targeted Hashim’s family this week, raiding his home and that of his parents. During the raid on his home last week, a woman believed to be his pregnant wife committed a suicide bombing, killing her unborn child and three other children. Reuters reported Sunday that men believed to be Hashim’s father and two brothers were killed in a shootout with police last week. Authorities have not clarified whether these interactions with the Hashim family have yielded any key evidence to prevent future attacks.

President Sirisena, Prime Minister Ranil Wickremesinghe, and Mahinda Rajapaksa – a former president Sirisena tried to illegally replace Wickremesinghe with in October, all attended Sunday Mass this weekend in a show of solidarity with Christians. Wickremesinghe claimed in the aftermath of the attack that he was never made privy to key intelligence indicating that jihadists were planning to attack churches on Easter; Sirisena banned Wickremesinghe and his cabinet from intelligence briefings following his attempt to make Rajapaksa prime minister. Sirisena has publicly claimed intelligence officials also failed to inform him of intelligence that may have prevented the attack.

Follow Frances Martel on Facebook and Twitter.