Sri Lanka's acting president renewed the country's state of emergency Monday ahead of a parliamentary vote to pick a new head of state -- a poll in which he is a leading candidate.
Ranil Wickremesinghe automatically became acting president when Gotabaya Rajapaksa resigned last week after fleeing to Singapore.
A state of emergency allows troops to arrest and detain suspects, and the president to make regulations overriding existing laws to deal with any unrest.
One was already in place but parliament had not met to ratify the declaration as required, and Wickremesinghe extended it from Monday "in the interests of public security", he said.
Police and the military, armed with emergency powers, stepped up security in the capital ahead of Wednesday's election of a new president.
Wickremesinghe, a six-time former prime minister, is being backed for the position by Rajapaksa's party, which remains the largest in the legislature.
In what was seen as a possible appeal to 14 Catholic legislators for their support, Wickremesinghe said he had asked Britain's help to complete investigations into the 2019 Easter Sunday bombings that killed 279 people.
Sri Lanka's small but influential Catholic minority believes the coordinated suicide attack against three churches and three hotels was a "political plot" to bring Rajapaksa to power, and has long sought an independent investigation.
Wickremesinghe was "requesting the assistance of the UK government and their intelligence services", his office said.
There was no immediate comment from the British High Commission.
The bombings were blamed on local jihadists and 25 men were indicted in October over alleged involvement.
But the Church and opposition parties claim state intelligence officers loyal to Rajapaksa directly or indirectly supported the bombers.
Rajapaksa was forced to flee last week when tens of thousands of protesters stormed his official residence after months of demonstrations across the country demanding his resignation over Sri Lanka's economic crisis.
The nation's 22 million people have been enduring severe shortages of essentials since late last year after the country ran out of foreign exchange to finance even the most vital imports.
The country defaulted on its $51 billion foreign debt in mid-April and is in talks with the IMF for a possible bailout.