Sixty people have been arrested so far in connection to the blasts

Highlights India had sent Sri Lanka detailed advisory that warned of suicide attacks

India gave name of group involved, its leader and other members

Three-page advisory mentioned group National Thowheeth Jama'ath

Ten days before the Easter bombings, India had sent Sri Lanka a detailed advisory that warned not only of the suicide attacks, but the group involved, the names of its leader and other members. 359 people had died and around 500 wounded in the string of bomb blasts on Sunday that targetted hotels and churches. So far, 60 people have been arrested after Sri Lanka blasts.

The three-page advisory, which has been accessed by NDTV, mentioned the group involved as the National Thowheeth Jama'ath. It had the whereabouts of those involved -- the addresses of their hideouts, phone numbers and background.

The document, dated April 11, had even mentioned the targets - churches and the Indian High Commission.

The wealth of information made action on it imperative, but none was taken, the Sri Lankan authorities have said.

In an interview to NDTV, Lankan Prime Minister Ranil Wickremesinghe had admitted that though they received an intelligence warning from India, "it was not conveyed down the line".

Sri Lankan President Maithripala Sirisena - who was out of the country during the attacks --has said he was not informed about this advisory and he has asked for the resignation of the country's defence secretary and police chief. Both officials report to the President.

The leader of Parliament and a minister in his government, Lakshman Kiriella, said the information was deliberately withheld, pointing at a swiftly developing political blame game.

Though ISIS claimed responsibility for the attacks, it has not provided any evidence to back it up, media reports said.

Three days on, the police have arrested 60 people for the attacks - government sources said the number might rise to 100. Investigators say there were nine bombers, one of them was a woman. Several of them were well educated and had travelled in foreign nations.