The PSC began hearing testimony from Muslim leaders who said they repeatedly warned the authorities to dangerous radicalisation. The committee summoned former governor of the Western province Azath Sally to testify before it.
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The cabinet meeting which is usually held on Tuesday mornings was not called by Sirisena, officials said.
President Sirisena on last week asked the Cabinet to halt the hearings, citing national security concerns.
Sirisena said that it was uncalled for and a serious threat to national security as the top intelligence personnel are identified through the media. He said he would not allow any serving defense official to testify before the PSC.
He wrote to Speaker Karu Jayasuriya urging a halt to the PSC.
Jayasuriya, however, replied that the PSC was a parliamentary issue and it would proceed.
Sirisena has insisted that as minister of defence and law and order he was unaware of precise intelligence warnings from India about the attack on April 21.
He suspended police chief Pujith Jayasundara and dismissed his top defence official Hemasiri Fernando after it was found that there were intelligence failures before the attacks.
Sirisena said that none of the serving officers would be authorised by him to testify in future.
Jayasuriya stressed that all officials are bound by parliamentary privileges and they would be compelled to respond to summons by the PSC.
Nine suicide bombers, including a woman, carried out a series of devastating blasts that tore through three churches and three high-end hotels frequented by tourists in the country's deadliest violence since the devastating civil war with the Liberation Tigers of Tamil Eelam ended in 2009.
The Islamic State claimed the attacks, but the government blamed local Islamist extremist group National Thawheed Jamaath (NTJ) for the bombings.
A three-member committee appointed to probe the attacks that killed 258 people, including 11 Indians, submitted its final report to President Sirisena on Monday. The details of the report were immediately not available.
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Sirisena's opposition to the PSC has triggered another clash between the executive and the legislature.
The president and his coalition partner, prime minister Ranil Wickremesinghe are at loggerheads and in October last year the president sacked the premier unconstitutionally.
The political and constitutional stand off lasted for nearly two months before Wickremesinghe was ordered to be restored by the Supreme Court.