After living through a bloody civil war that dragged on for three decades, the people of Sri Lanka are no strangers to terror.

But the carnage that unfolded yesterday saw the country’s enemies take on new depths of depravity.

It had all the hallmarks of the barbaric Islamic State group – executed meticulously and without mercy.

Within minutes of yesterday’s blasts, MI5 was trying to establish if there were any British links to those who could be behind the plot. There were no immediate claims of responsibility, nor any established motive for the attack, although 13 suspects had been arrested by last night.

Early evidence pointed to the National Thowheed Jamaath (NTJ), a relatively unknown radical Islamist group said to have formed in Kattankudy, a Muslim-dominated town in eastern Sri Lanka, in 2014.

Alex and Anita Nicholson photographed in London in 2015. Both were killed in the bomb blast in the Shangri-La hotel

Last photo: Shantha Mayadunne (second left) and her daughter Nisanga (right) were among the victims of the Sri Lanka bomb attacks on Sunday. The family posted this picture of their Easter breakfast at the Shangri-La hotel just before the blast there

A map showing where the eight blasts went off today, six of them in very quick succession on Easter Sunday morning

ISIS militants marching in Raqqa, Syria, in 2014. This year the fundamentalists were driven from the last land they occupied but security experts have warned of 'pop up' terror cells

It has no history of mass fatality attacks.

In fact, its only mention appears to be last year when it was linked to the vandalism of Buddhist statues.

Sources in the Muslim community in Sri Lanka claim the group has publicly supported Islamic State. They also say that Zahran Hashim, named in reports as one of the bombers, was its founder.

Although intelligence files on the group are small, there is no doubt the warning signs were there.

On April 11, Sri Lankan police circulated a document entitled ‘Information of an alleged plan attack’ which said they had been warned by an unnamed foreign intelligence agency that the NTJ was plotting suicide attacks on churches in Colombo.

It added that intelligence pointed to any of the following methods: suicide attack, weapon attack or truck attack.

The original warning is most likely to have come from Australia – one of the ‘five eyes’ with a close intelligence-sharing relationship with Britain – that has kept watch on the rise of extremism in the region.

Documents show that Sri Lanka’s police chief Pujuth Jayasundara then issued an intelligence alert to top officers, specifically warning that suicide bombers planned to hit ‘prominent churches’.

Sri Lanka's defence ministry has now ordered curfew with immediate effect 'until further notice', and the Sri Lankan government said it had shut down access to social media messaging services, sources say

Hospital staff push a trolley with a casualty after an explosion at a church in Batticaloa, Sri Lanka

A crime scene official inspects the site of a bomb blast inside a church in Negombo, Sri Lanka, which lost half its roof tiles with the force of the blast

Documents even named six individuals as likely suicide bombers, including Hashim. Yesterday, the seemingly far-fetched plan became frighteningly real.

Why the police did not sound the alarm earlier will remain a mystery. Prime minister Ranil Wickremesinghe admitted that information about the attacks had been received in advance but denied having direct knowledge himself. ‘We must look into why adequate precautions were not taken. Neither I nor the ministers were kept informed,’ he said following intense anger in the community.

Whichever group was behind yesterday’s attack, it was most certainly inspired by the tactics used by IS. The suicide bombings explicitly targeted civilians, designed to create maximum terror for maximum effect – like the Manchester Arena bombings and the London Bridge attack.

They also chose iconic locations packed full of people, including many foreigners.

IS – which lost its final sliver of territory in Syria just weeks ago – also has a history of staging attacks against Christians on holy days, notably Christmas and Easter.

British military chiefs and ministers have long warned that the defeat of the terror group in the Middle East does not mean it has been vanquished.

They have referred to a ‘pop-up’ IS involving the group emerging elsewhere, often in states where they can exploit a vacuum. They have specifically warned of the rising threat from such diehard jihadis in south-east Asia.

IS fostered a brand which was so effective other terror groups wanted to be associated with it.

Some radicalised Muslims travelled from Sri Lanka to Syria to fight in that country’s civil war.

In 2016, the justice minister said 32 Sri Lankan Muslims from ‘well-educated and elite’ families had joined IS in Syria.

The recent loss of its last territory makes it even more likely that foreign fighters from countries such as Sri Lanka may now be returning home.

Terrorism expert Raffaello Pantucci says the demise of the group’s ‘caliphate’ could have persuaded extremists to stay in their countries and mount attacks there instead. ‘Think how big Islamic State’s footprint is,’ he said. ‘This means it has a reverse effect as well – their ideas are going out to a big pool of places.’

Sri Lankan military stand guard near the explosion site at a church in Batticaloa,with police tape keeping out bysanders

Security forces inspect the St. Anthony's Shrine after an explosion hit St Anthony's Church in Kochchikade in Colombo

State minister of defence Ruwan Wijewardene said investigators have identified the culprits behind the 'terrorist' attacks (pictuerd: Shangri La hotel, Colombo)

Yesterday’s bombings end a decade of relative peace in Sri Lanka following the end of its civil war in 2009. Terrorist bombings were common during the brutal 25-year struggle during which the Sri Lankan government fought Tamil separatism.

But despite the period of calm, much bitterness and grievance has remained in the country, riven by ethnic disputes.

Sri Lanka, which is mainly Buddhist, does not have a recent history of persecution of its Christian minority, which comprises 7 per cent of the population.

Yet its relations with others, including Hindus and Muslims, have not always been easy. Over the years there has been an increasing rise of discontent among Sri Lanka’s Muslim community, which make up 10 per cent of the population.

In November 1990, many were expelled from their homes in the north and have since been living as ‘displaced’ in the southern part of the country, under the patronage of the state.

Whatever the motives behind yesterday’s attack, there is little doubt that the brutal tactics used by Islamic State will continue to inspire others.