He made the remarks on Monday before the Presidential Commission of Inquiry (PCoI), which is probing the terror carnage, the Daily Financial Times newspaper reported.

"If I had been briefed of these intelligence reports, I would have called off my overseas trip and taken all measures to prevent such heinous attacks from taking place. This calamity could have been averted if those entrusted with the responsibility of following up on intelligence reports had done their job diligently," Sirisena told the the COI during nearly six hours of questioning by the Attorney General's representative to the Commission Additional Solicitor General Ayesha Jinasena P.C.

The COI was appointed on September 20, 2019 by Sirisena when he was in office, Its term has been extended till December 20 this year by incumbent President Gotabaya Rajapaksa.

Sirisena further said that he had left the country on April 16, 2019 for Singapore with a stopover at Tirupati, India, noting that it was during his absence the unfortunate incidents took place and that he had been kept in the dark on the serious threat facing the country.

He said before the trip, he had held meetings with then IGP Pujith Jayasundera, former Defence Secretary Hemasiri Fernando, chief of the State Intelligence Service (SIS) and other and senior police officers.

"At none of these meetings was I told of the foreign intelligence report received on 4 April with a specific threat of terrorist attacks," the Daily Financial Times newspaper quoted the former leader as saying.

Had he been aware of the intelligence report, "I would have focused all attention on dealing with such a threat".

"I would have informed the Cardinal and consulted with the security establishment to have these attacks stopped. These incidents are the worst black mark in my political career and personally it has left me greatly aggrieved."

Sirisena is expected to continue providing evidence before the COI till October 12, while former Prime Minister Ranil Wickremesinghe will appear before it on Tuesday.

The former President's remarks came after Jayasundara told the PCoI late last month that Sirisena should take the sole responsibility of the well-planned carnage, reports The Daily Mirror newspaper.

The former IGP said that although he had given specific instructions about the possible terror attack to all the senior police officers, during investigation it was found that all his call records were deleted.

On April 21, 2019, three churches in Negombo, Batticaloa and Colombo and the hotels -- Shangri-La, Cinnamon Grand, Kingsbury and Tropical Inn -- in the capital city were targeted in the series of coordinated suicide bombings, which killed over 250 people and injured more than 500 others.

Sri Lankan authorities attributed the attacks to little-known local Islamist extremist groups, National Thowheeth Jama'ath and Jammiyathul Millathu Ibrahim.

However, the Islamic State terror group claimed the attacks.