New Delhi: Sri Lanka has put all the police stations in Colombo on high alert following reports of a lorry and a van carrying explosives on Tuesday, two days after the country was rocked by eight serial explosions causing large scale devastation and killing 321 people.

Police sources have said that a fourth planned Sri Lanka hotel attack has been foiled, news agency AFP reported on Tuesday noon.

On Monday, one more blast had taken place in the capital of the island nation as the bomb squad members were trying to defuse a device. Reports said that as many as 87 bomb detonators were found in Colombo on Monday.

Shangri-La Hotel closed until further notice:

Meanwhile, the five-star Shangri-La Hotel in Colombo which was one of the five hotels where blasts occurred, will be closed till further notice, news agency PTI reported quoting hotel official. The hotel which is frequented by tourists and foreigners saw the death of unspecified number of guests, including Indians in the blast.

"It is with great sadness that we can confirm that we are aware of a number of casualties among our guests and colleagues. This includes three of our colleagues who were fatally injured in the course of their duties," the hotel said in a statement.

Must Read: Islamic State claims responsibility for Easter Sunday bombings in Sri Lanka

"We will continue to work closely with local authorities and emergency services to provide our fullest assistance and support to all affected parties. Our hotel remains secured by the military and the police. We have also decided that the hotel will be closed until further notice," the statement said.

The hotel announced that they will continue to provide alternative accommodation for their affected guests. A dedicated helpline (+603 2025 4619) has been set up for affected guests and/or their loved ones.

"We are working closely with relevant embassy officials to support their respective citizens," the hotel said in the statement.

At least five Indians were killed when the suicide bomber struck the hotel.

The Indian High Commission in Colombo identified them as, Lakshmana Gowda Ramesh, K M Lakshminarayan, M Rangappa, K G Hanumantharayappa and Narayan Chandrashekar. Four of them were workers of the Janata Dal (Secular) party.

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 321 people and wounding 500 others, including Indians, in the country's worst terror attack.

The Islamic state has claimed responsibility for the attacks on Tuesday evening. Police have so far arrested 24 people - mostly members of the NIJ - in connection with the blasts.