COLOMBO - Investigations by Sri Lankan police have confirmed that nine suicide bombers were involved in Sunday's attacks, eight of whom have been identified, State Defense Minister Ruwan Wijewardene said on Wednesday.

The leader of a local extremist group that carried out the bombings was one of the suicide bombers, the minister told a press conference.

Wijewardene said, so far 60 suspects had been arrested over the explosions and 32 of them had been handed over to the Criminal Investigations Department.

He said massive hunts were continuing to nab more suspects and vowed to bring the situation under control in the coming few days.

"We are asking people to be vigilant. There could still be a few people out there. But within the next few days we will have the situation under control," Wijewardene said.

Giving further details on the attackers, Wijewardene said that one of the bombers had pursued an education overseas and almost all were from stable financial backgrounds. "The fact that they were from good financial backgrounds is a worry for the government," he said.

He said all the suspects who had been taken in for questioning were locals and no foreign national was in custody.

Attackers belonged to a group which had broken away from another group called the National Tawheed Jamaat, and this group had caused minor violence by vandalizing Buddhist statues and attacking temples, in the recent past, according to the minister.

He said they had received international assistance to conduct more probes and very soon all those involved would be arrested.

Following claims that Islamic State was behind the attacks, the minister said investigations were ongoing to see if these claims were true and whether the IS had financially funded the attackers.

He further said there had been serious security lapses as despite the intelligence having prior information of possible suicide attacks, no adequate measures had been taken.

The minister said President Maithripala Sirisena was looking into this.

The death toll from Sunday's eight explosions has risen to 359 including 34 foreign nationals.

The country remains under a conditional state of emergency since Tuesday.