Sri Lanka will conduct a house-to-house search of the entire country to root out terrorists in the aftermath of the Easter Sunday bombings, the president said on Friday, as he accused security officials of failing to act on warnings that an attack was imminent.Seeking to deflect blame for the intelligence failure, President Maithripala Sirisena vowed a “total reorganization” of Sri Lanka’s security apparatus and argued that the prosecution of military intelligence officers for abuses during the country’s long civil war had left the nation vulnerable. He promised a get-tough approach that he likened to the campaign against Tamil rebels in that war.“Every household in the country will be checked,” Mr. Sirisena said in a meeting at his official residence with the heads of Sri Lankan media organizations, according to a statement released by his office. “The lists of permanent residents of every house will be established to ensure no unknown persons could live anywhere.”Mr. Sirisena, who is also defense minister, has faced intense criticism since a series of coordinated bombings at churches and hotels that killed more than 250 people. Sri Lankan security officials had written a memo 10 days before the attacks describing the threat of bombings, with names, addresses and phone numbers of those believed to be involved, but the president and prime minister say the warning never reached them.Mr. Sirisena vowed to take action against anyone who failed to prevent the attack, putting particular blame on two officials: the defense secretary, Hemasiri Fernando, who resigned on Thursday, and the inspector general of the police, Pujith Jayasundara, who was expected to step down on Friday.“They did not say a word about this warning letter,” Mr. Sirisena said. “It was a serious lapse on their part and shirk of responsibility.”The Sri Lankan government has been consumed by months of infighting, and Prime Minister Ranil Wickremesinghe, a rival of the president, complained that he was excluded from security meetings.[ISIS reminded the world that it does not need to control territory to be a major threat.]A local Islamist extremist group is said to have carried out the bombings, and some people linked to the plot are still at large, officials said. Images posted online appear to show the Sri Lankans pledging allegiance to the Islamic State, which has claimed responsibility for the attacks, though its exact role is not clear.Mr. Sirisena said that security forces were making widespread arrests, and that more than 70 people had been held so far. He said he believed there were as many as 140 supporters of the Islamic State in Sri Lanka, according to news reports on his meeting.Sunday Masses at Sri Lanka’s Roman Catholic churches are suspended until further notice, the archbishop of Colombo, Malcolm Ranjith, said Friday. Many mosques were not holding Friday prayers.Hundreds of police officers scoured the capital on Thursday looking for three men and three women who are believed to be connected to the bombers and possibly planning new attacks.A growing number of foreign governments have warned their citizens about increased risks in Sri Lanka. On Friday, Britain advised “against all but essential travel to Sri Lanka.” Thailand warned its citizens to avoid religious centers from Friday though Sunday.In his comments on Friday, Mr. Sirisena cast blame widely, saying his campaign against illegal drugs might have been a factor in the attacks because of the connections between drug gangs and terrorism. Thus far, no evidence has emerged of connections between the local extremist group believed to have carried out the bombings — National Thowheeth Jama’ath — and illegal drugs.Mr. Sirisena also said that Zaharan Hashim, the head of National Thowheeth Jama’ath, is believed to have died while carrying out the bombing of the Shangri-La Hotel. Mr. Zaharan appeared in a video with seven masked men declaring allegiance to the Islamic State.In a dig at Mr. Wickremesinghe, the prime minister, the president said the intelligence failures may have occurred partly because the security agencies had been weakened by a crackdown on human rights abuses committed during the country’s civil war, which ended in 2009.Mr. Sirisena has cast himself as a protector of the security apparatus, and accused his opponents of undermining the country’s national defense. He added that his support of the armed forces was one of the reasons for his rift with the prime minister and his cabinet, according to News First, a Sri Lankan news outlet.It reported the president as saying that he had felt compelled to send top intelligence officers overseas to protect them from harassment.