The father and two brothers of the suspected mastermind of the Easter Sunday terrorist attacks in Sri Lanka have been killed in a gun battle after security forces stormed a house on the country’s east coast.

Zahran Hashim, who blew himself up at a hotel in Colombo during the bombings, is believed to have organised the attacks in which at least 250 people were killed. He was also the founder of Islamist group the National Thowheed Jamath (NTJ), which has now been banned.

His father and brothers were among 15 people killed on Friday. Zainee Hashim, Rilwan Hashim and their father Mohamed Hashim had appeared in a video circulating on social media calling for all-out war against non-believers.

They were shot as troops moved in on their house after a tip-off from locals.

As gunmen opened fire at the approaching security forces, three other men in the building detonated bombs, killing themselves along with six children and three women. Three more people died in the shooting.

Two people who were inside the house, a woman and a seven-year-old girl believed to be relatives of the men, survived, Reuters reports.

Sri Lanka: Scene of the bomb attacks and aftermath Show all 38 1 /38 Sri Lanka: Scene of the bomb attacks and aftermath Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan Special Task Force officers raid a house following an explosion in capital Colombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A blood-spattered statue of Jesus Christ while crime scene officials inspect the site of a bomb blast, as the sun shines through the blown-out roof, inside St Sebastian's Church in Negombo Reuters Sri Lanka: Scene of the bomb attacks and aftermath A police officer inspects the damage after a bombing at the Shangri-La Hotel in Sri Lankan capital Colombo AP Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan soldiers look on inside the St Sebastian's Church at Katuwapitiya in Negombo following a bomb blast during the Easter service AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A woman cries next to a coffin of a bomb blast victim. A series of eight devastating bomb blasts ripped through high-end hotels and churches holding Easter services in Sri Lanka on April 21, killing more than 300 people AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath People who live near the church that was attacked the day before, leave their houses as the military try to defuse a suspected van before it exploded in Colombo Reuters Sri Lanka: Scene of the bomb attacks and aftermath Shoes and belongings of victims are collected as evidence at St Sebastian's Church AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan police were forded to clear an area while Special Task Force Bomb Squad officers inspected the site of an exploded van near a church the day after it was attacked Reuters Sri Lanka: Scene of the bomb attacks and aftermath The Kingsbury Hotel in Colombo, Sri Lanka following a bombing AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Queues at the National Blood Bank in Colombo, Sri Lanka after a request for blood to aid in recovery efforts Mr Lavasquabble/Twitter Sri Lanka: Scene of the bomb attacks and aftermath Medical response team work to remove dead bodies from the scene of bombings in Sri Lankan capital Colombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan security personnel inspect the debris of a car after it exploded when police tried to defuse a bomb AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Security personnel work at the scene of a bombing at a church in Batticaloa in Sri Lanka AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A woman is helped near St Anthony's Shrine after a blast in Colombo, Sri Lanka, on Sunday 21 April 2019. At least 130 people were killed and more than 500 hospitalised after near-simultaneous explosions hit three hotels and three churches on Easter Sunday. AP Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan police officers clear the road as an ambulance drives through carrying injured of church blasts in Colombo, Sri Lanka, on Sunday 21 April 2019 AP Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan soldier stands guard near a car explosion AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A woman prays at St. Sebastian's Church in Negombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Priests stand inside St Anthony's Shrine, Kochchikade church on the outskirts of Colombo after a bombing Reuters Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan woman living near St. Anthony's shrine runs for safety with her infant after police found explosive devices in a parked vehicle in Colombo AP Sri Lanka: Scene of the bomb attacks and aftermath People react during a mass for victims, two days after a string of suicide bomb attacks on churches and luxury hotels Reuters Sri Lanka: Scene of the bomb attacks and aftermath Security personal react as a device was detonated in a controled explosion in a van near the St Anthony's Church EPA Sri Lanka: Scene of the bomb attacks and aftermath Security forces inspect the scene of a bombing at the Shangri-La Hotel in Sri Lankan capital Colombo Getty Sri Lanka: Scene of the bomb attacks and aftermath The Kingsbury hotel in Colombo, Sri Lanka after a bombing attack Getty Sri Lanka: Scene of the bomb attacks and aftermath The damaged interior of a church in Negombo, Sri Lanka following a bombing attack Reuters Sri Lanka: Scene of the bomb attacks and aftermath Police and security personnel stand guard outside the Shangri-La Hotel in Sri Lankan capital Colombo following a bombing attack EPA Sri Lanka: Scene of the bomb attacks and aftermath Debris is seen at St Anthony's Church in this still image from video footage after explosions hit churches and hotels in Colombo, Sri Lanka, on 21 April 2019 Derana TV/via Reuters Sri Lanka: Scene of the bomb attacks and aftermath Damage inside a church following a bombing attack AP Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan Special Task Force officer scales a house during a raid following an explosion in capital Colombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A general interior view showing damage after an explosion hit St Anthony's Church in Kochchikade, Colombo, Sri Lanka, on Sunday 21 April 2019 EPA Sri Lanka: Scene of the bomb attacks and aftermath Priests walk into St Anthony's Shrine Kochchikade church after an explosion in Colombo, Sri Lanka, on 21 April 2019 Reuters Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan police officer stands outside St Anthony's Shrine in Colombo, Sri Lanka, after a blast on Sunday 21 April 2019 AP Sri Lanka: Scene of the bomb attacks and aftermath A shoe of a victim is seen in front of the St Anthony's Shrine, Kochchikade Church Reuters Sri Lanka: Scene of the bomb attacks and aftermath Local and security officials gather at the scene at St Anthony's Church in Kochchikade, Colombo, Sri Lanka EPA Sri Lanka: Scene of the bomb attacks and aftermath An ambulance is seen outside the church premises with gathered security personnel following a blast at St Anthony's Shrine in Kochchikade, Colombo, on Sunday 21 April 2019 AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Armed policemen patrol the area after an explosion hit at St Anthony's Church in Kochchikade in Colombo, Sri Lanka, 21 April 2019 EPA Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan Army soldiers secure the area around St. Anthony's Shrine after a blast in Colombo, Sri Lanka, Sunday 21 April 2019 AP Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan security personnel keep watch outside the church premises following a blast at the St Anthony's Shrine in Kochchikade, Colombo, on Sunday 21 April 2019 AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Police officers inspect the scene after an explosion hit at St Anthony's Church in Kochchikade in Colombo, Sri Lanka, 21 April 2019 EPA

According to locals, two men had moved into the three-room rented house in the Sainthamaruthu area of Kalmunai, days before the Easter Sunday attacks.

When more people arrived, neighbours grew suspicious, Mohammed Majid, secretary of the Grand Masjid Sainthamaruthu mosque, told Reuters.

After evening prayers on Friday, a group of men from the local Hijra mosque came to the house to question the occupants.

When one man brandished an assault rifle, the men fled, alerting police, who arrived shortly afterwards. One man was killed after running into the street with a gun to confront police, before a series of explosions came from the house, witnesses said.

A police officer inspects the site of a gun battle between troops and suspected Islamist militants (Reuters)

A police officer inspects the site of a gun battle between troops and suspected Islamist militants (Reuters)

As the investigation into the Easter Sunday attacks continues, Sri Lankan authorities believe more suicide bombers could be planning attacks. So far the focus has been on two domestic groups believed to have been behind the bombings – the NTJ and Jammiyathul Millathu Ibrahim.

After Friday’s violence, police also seized an Isis flag from another property nearby, where locals said they feared further attacks.

The country has been on high alert since the Easter Sunday bombings, with nearly 10,000 soldiers deployed across the island to carry out searches and hunt down members of two local Islamist groups believed to have carried out the attack.

Authorities have detained more than 100 people, including foreigners from Syria and Egypt, since the 21 April bombings.