Image copyright EPA Image caption Security is tight in the aftermath of the attacks

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

It blamed a calculation error and the difficulty of identifying victims.

Scores were killed and hundreds injured when suicide bombers struck hotels and churches in Colombo, Negombo and the eastern city of Batticaloa.

Most of those killed were Sri Lankan but dozens of foreigners were also among the 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:

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

Sri Lankan police apologised after mistakenly releasing a photo of US-based student activist Amara Majeed as one of the suspects

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

Members of the Pakistani Ahmadi Muslim community, as well as some Christians and Afghan nationals, have been ejected from their homes in the city of Negombo. Rights activists warned they could face reprisal attacks

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

Media playback is unsupported on your device Media caption Ramesh was killed in the blast in Batticaloa

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 change in the death toll is unlikely to help.

The downward revision means this no longer ranks as the deadliest attack claimed by IS.

What is the security situation in Sri Lanka now?

At least seven suspects are still identified as being at large.

Fears of further attacks means that Sri Lanka remains a country on edge, with nightly curfews and security forces making sweeps across the nation, in an effort to root out all connections with the attacks.

Over the last few days, a clearer picture has also built up of the bombers, who officials said were well off and well educated and at least one had spent time abroad in the UK and Australia.

Thursday saw offices in central Colombo shut early and workers told to go home as well as a brief lockdown in part of the capital because of bomb scares.

Rumours and false alarms have also been making the rounds over the past few days.

Added to that is the ever-present fear of communal violence and reprisals against Muslims in Sri Lanka.

What about the Muslim minority?

Some Muslims in Sri Lanka report feeling fearful and several Muslim organisations have advised worshippers to stay at home for Friday prayers.

In Negombo, a community of refugees and asylum-seekers, mostly belonging to the Ahmadi minority sect from Pakistan, but also including some Christians and Afghan nationals, have been ejected from their homes by landlords.

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

This community of refugees fled persecution and had been sheltering in Sri Lanka - human rights activists say they are likely to have been targeted largely for being both foreign and Muslim.

Sri Lanka has a sizeable and centuries-old Muslim population - out of 21 million, just under 10% are Muslim.

During Sri Lanka's civil war they were subject to several brutal assaults, and in the years since there has been sporadic violence against Muslims, largely by Sinhalese Buddhists.

A community in fear

Muralitharan Kasiviswanathan, BBC Tamil, Negombo

As of Wednesday, more than 600 Ahmadis had taken refuge at Faizul Mosque in Negombo, one of the five Ahmadi mosques in Sri Lanka.

Most of the Ahmadis were renting their homes from Catholic Christians. Although the bomb blasts happened on Sunday, it was three days later that things got scary for the Ahmadis.

"My home is some streets away from the church. After the attack, the owner of my house was very worried and asked me to be safe somewhere. I am paying 13,000 rupees [£58; $74] for that house. Most of us paid a year's rent an advance. Where will we go now?" asks 27-year-old Habis Rabba Soaib.

About 800 Ahmadis from Pakistan live here with the help of the UN refugee agency, UNHCR. Fearing religious prosecution, they fled Pakistan and came to Negombo and hope to eventually seek asylum in Europe or the US.

Although the Faizul mosque is small, officials are taking care of them and it is being guarded by the army and the police.

More than 5,000 native Ahmadis live in Negombo. Many of them have lived here for years and now own houses and businesses.

"Since we have been here for a long time, nobody is threatening us," says one of the Muslim youths who is busy helping the Pakistanis.