Elim Tamil Church, which meets at a school near Woodgrange Park, said family members of a small number of its members were among the dead.
Senior Pastor Daniel Stanley told Premier: "It's absolutely devastating.
"Ten years after civil year, we did not even imagine these kinds of attacks would take place again and that these kinds of tragedies would take place again."
Nine explosions - including seven by suicide bombers - have left almost 300 people dead, according to senior Sri Lankan authorities.
Eight Britons are thought to be among the dead. Twenty-four suspects are in custody, officials say.
Blasts struck three churches - St Anthony's Shrine in Colombo, St Sebastian's in Negombo and at Zion Church in the eastern town of Batticaloa.
On this holy day, let us stand with the people of Sri Lanka in prayer, condolence and solidarity as we reject all violence, all hatred and all division.— Archbishop of Canterbury (@JustinWelby) April 21, 2019
The Cinnamon Grand, Kingsbury and Shangri-La hotels were among other locations targeted.
Pastor Stanley said he had personally checked with everyone at his church to find out whether they had been affected.
He added: "We can't take this again after ten years of civil war. This has to be stopped and every spirit of terrorism has to be stopped.
"Just kneel down and pray earnestly for the people of Sri Lanka."
The acts of violence against churches and hotels in Sri Lanka are truly appalling, and my deepest sympathies go out to all of those affected at this tragic time.— Theresa May (@theresa_may) April 21, 2019
We must stand together to make sure that no one should ever have to practise their faith in fear.
Local militant group National Thowfeek Jamaath was accused by the Sri Lankan health minister on Monday of being responsible for the bombings.
Click here to listen to Premier's Alex Williams speaking with Pastor Daniel Stanley:
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