Sri Lankan Prime Minister Ranil Wickremesinghe said on Tuesday that there had been prior intelligence warnings about the attacks in the country, including on the Indian High Commission in Colombo.
Talking to reporters, he also said that there will be changes in the top positions of the security establishment following the deadly Easter Sunday suicide bombings which killed 359 people and injured over 500.
Earlier addressing Parliament, he said investigators have made good progress identifying the suspects and that some of the bombers travelled abroad and then returned home.
He said "it was possible" the bombings were a "retaliation" for the New Zealand mosque attacks that left 50 Muslims dead and were blamed on a white supremacist from Australia. Defence Minister Ruwan Wijewardene made similar remark earlier in the day.
Wickremesinghe said that Sri Lanka has been offered assistance by many countries and international organisations, including the UN, the Interpol, to combat terrorism.
Defence Secretary Hemasiri Fernando said Tuesday that the FBI has already commenced investigations into the incident while the Interpol is expected to arrive in the country.
He also pointed out that the recent attacks targeted the country's economy and also the tourism industry. Accordingly, the government has taken steps to implement a special plan in order to protect the tourism industry, he said.
Seven suicide bombers believed to be members of an Islamist extremist group - the National Tawheed Jamath (NTJ) - carried out a series of devastating blasts that tore through three churches and luxury hotels in Sri Lanka on Easter Sunday, killing 359 people and wounding more than 500 others, including Indians, in the country's worst terror attack.
The Islamic State has claimed responsibility for the devastating blasts and identified the seven suicide bombers who were involved in the attacks.
Forty suspects, including the driver of a van allegedly used by the suicide bombers, have been arrested so far in connection with the attacks that shocked Sri Lankans who observed a day of national mourning on Tuesday.
National flags were lowered to half mast and people bowed their heads as a three-minute silence began at 8:30 am local time, the time the first of the attacks occurred on Sunday.