In an act of defiance, priests in Sri Lanka have held the country’s first public mass since the Easter Sunday bombings in a bid to show they will not be cowed by militants. As warnings of imminent further attacks remain in place, President Maithripala Sirisena revealed that a foreign mastermind could have planned the atrocities as part of a new strategy by ISIS to target smaller countries. The coordinated attack on churches and luxury hotels, which killed more than 250 people, led to the suspension of public mass to protect congregations. But on Tuesday, surrounded by a heavy military presence, the first mass was held during a pre-planned ordination of a priest in Thannamunai, on Sri Lanka’s east coast. More than 80 Sri Lankan priests attended in a show of unity against extremism. Father Norton Johnson said: "People wanted to celebrate Mass, they wanted to participate in this, but they – even myself – were afraid. "However, security personnel gave us good protection." With fears of further planned attacks, Saudi Arabia has now become the latest nation to urge its citizens to leave Sri Lanka. On Twitter the embassy said: "Due to the current security situation in the Republic of Sri Lanka, the embassy advises citizens in Sri Lanka to leave." It follows news that eight government ministers have been warned they could be targeted by terror suspects who are still at large. Sri Lanka's health minister, Rajitha Senaratne, said intelligence officials had warned him he was one of them and had advised him to remain at home. Some security measures are steadily being relaxed, with a social media ban in the country being lifted. The government introduced it in the aftermath of the attacks to curb the spread of fake news. In a statement, Mr Sirisena urged those using social media to continue to "act in a responsible manner". But a ban on women wearing face coverings remains in force. Security forces have widened a hunt for those responsible, with raids in India resulting in the arrest of a 29-year-old man who told officials he was a follower of Mohammed Zaharan, the Sri Lankan militant who officials say led the Easter attacks. On Monday, investigators claimed the man, named as Riyas Aboobacker, was allegedly plotting a similar suicide attack in the southern Indian state of Kerala. Sri Lankan authorities had initially blamed Zaharan and his followers alone for the attack, but two days later ISIS claimed responsibility as it released images of Zaharan and others pledging their allegiance to ISIS leader Abu Bakr Al Baghdadi. In a video released on Monday, a man said to be Al Baghdadi praised the suicide bombings in Sri Lanka, calling them "part of the revenge" that awaits the West. It was his first filmed appearance in five years. In Bangladesh, security forces are investigating claims by ISIS that it was responsible for an explosion at a shopping centre in the capital that injured three police officers. Police said a "very powerful" crude bomb thrown by unidentified assailants in Dhaka on Monday injured two traffic officers and a community police officer. The belated crackdown on extremists comes after it was revealed that some Sri Lankan officials failed to act on warnings that terror attacks were being planned. Since the news, the government has announced a major shake-up and raids in the country have seen more than 100 people arrested. Officials say 140 militants with links to ISIS have been identified as raids to apprehend them continue.