New Delhi: Even as India gave specific intelligence inputs to Sri Lanka about a possible attack, Colombo did not take "adequate precautions" to prevent the explosions that killed 218 people and injured at least 450 in the decade's worst terror strike.

Prime Minister Ranil Wickremesinghe on Sunday accepted that they had information regarding a possible attack but did not take adequate steps to prevent it.

According to top intelligence sources, Zahran Hasim of National Thowheed Jama'ath of Sri Lanka and his associates had hatched a plan to carry out an Istishhad (suicide attack) in the island country. They had also conducted a dry run and deployed an explosives-laden motorcycle at Palmunai near Kattankudy on April 16 as a part of their plan.

Sources further said that they had planned to carry out an attack on or before April 22. They had reportedly selected eight places, a church and a hotel, where Indians came in large numbers. New Delhi had shared the information with Colombo on April 4.

Acting on the information, Sri Lanka's police chief Pujuth Jayasundara had sounded a nationwide alert 10 days before the Sunday's attack. "A foreign intelligence agency has reported that the NTJ (National Thowheeth Jama'ath) is planning to carry out suicide attacks targeting prominent churches as well as the Indian High Commission in Colombo," said the alert.

Addressing the media after the attack, PM Wickremesinghe said that they would need assistance to ascertain if the terrorists responsible for the attacks received help from overseas. He, however, added that according to the information he has received till now, the suspects are local.

Thirteen people have been arrested in connection with the eight blasts. Wickremesinghe said that police would soon release the names of people behind the attack.

Meanwhile, Sri Lanka president Maithripala Sirisena has appointed a Special Investigation Committee to look into the causes and consequences of the attack. The Presidential Secretariat stated that the panel of judges, including a Supreme Court judge, will look into the matter. The panel has been asked to submit a report within two week.