Sri Lanka has revised down the death toll from Sunday's blasts by more than 100, to "about 253", the health ministry says.

It has blamed a calculation error.

Suicide bombers struck hotels and churches in the Colombo area and the eastern city of Batticaloa. Hundreds were injured, officials said.

Most of those killed were Sri Lankans, but dozens of foreigners were also casualties. Nine people are suspected of carrying out the attacks.

Police have continued carrying out raids and have issued photographs of seven people wanted in connection with the attacks.

The authorities blamed a local Islamist extremist group, National Thowheed Jamath (NTJ), soon after the blasts but say the bombers must have had outside help.

The Islamic State group said it was behind the attacks and published a video showing eight men but provided no evidence of direct involvement.

In other developments:

-Hundreds of Muslims, fearing revenge attacks, have been fleeing the city of Negombo, site of one of the attacks

-Sri Lanka's defence secretary, Hemasiri Fernando, the top non-elected official at the department, announced his resignation on Thursday in response to intelligence failures

-The country's Catholic Church has announced the suspension of all church services

-Police say more than 70 people have now been arrested

-The UK Foreign Office is now warning against all but essential travel to Sri Lanka

Why was the wrong toll given?

Sri Lankan Deputy Defence Minister Ruwan Wijewardene said morgues had provided inaccurate figures.

Another official, the head of health services, told Reuters news agency there had been so many body parts it was "difficult to give a precise figure".

According to the health ministry, all autopsies had been completed late on Thursday and it transpired that some victims had been counted more than once.

BBC World Service South Asia editor Jill McGivering says the revised figure comes as the government is struggling to restore its credibility - amid criticism of its apparent failure to respond to intelligence warnings before the attacks.

It's also battling to counter fake news and false rumours about the crisis, she says. This sudden dramatic revision is unlikely to help.

What is the situation with the Muslim minority?

Muslims in Sri Lanka are reporting feeling fearful and say they are facing persecution.

Many of those in Negombo belong to a minority sect, the Ahmadi. Some have been sheltering in a mosque under police protection.

Ahmadi Muslims identify as Muslim and follow the Koran, but are viewed by many orthodox Muslims as heretical.

Many of those living in Sri Lanka have fled from persecution elsewhere, including Pakistan.

Prime Minister Ranil Wickremesinghe has admitted that some Ahmadis have been subject to attacks. Of Sri Lanka's 21-million population, just under 10% are Muslims.