Twenty people have been injured in a suspected bomb blast at an apartment block in Sweden.
The explosion reverberated through downtown Gothenburg at 5am, sending terrified residents fleeing to the exits as others clambered onto the balconies of neighbouring flats to escape the smoke pouring through their front doors.
Police initially expressed scepticism that the blast was the result of an accident, ruling out a gas leak, and the bomb squad remained on hand as firefighters spent hours extinguishing the resulting blaze.
Detectives have since said that they believe that an explosive device could have been used at the building, although no bomb has yet been found.
A police officer who recently testified in a major gang trial in Sweden's second city lives in the building, newspaper Goteborgs Posten reported.
'Obviously we will look into this,' the officer, whose name was not disclosed, told the paper.
Three women, aged between 60 and 80, and a man, were among the most seriously wounded.
Smoke pours out of apartment windows after an explosion struck the apartment block in the city of Gothenburg at around 5am
Smoke billows out of windows after the explosion in the Annedal area of central Gothenburg
Firefighters appear to be trying to gain access to a nearby building this morning
Paramedics take an injured person away on a stretcher. As many as 25 have been hospitalised
Smoke pours from the building as a fire engine cherry picker helps to extinguish the blaze
Interior Minister Mikael told a joint press conference with Prime Minister Stefan Lofven: 'It's obvious that a crime cannot be excluded.'
Lofven, whose government has been criticised in recent years for failing to rein in rising gang crime, told reporters he did not want to 'speculate' on the origin of the explosion.
'Everyone should know that society is always stronger than crime,' the PM told the press conference.
The blast triggered a fire which took firefighters several hours to extinguish.
'The site has been closed off and rescue operations are underway,' western regional police spokesman Hans-Jorgen Ostler said.
'As soon as the site is secured, we will begin a technical investigation to determine the cause of the fire and explosion,' he added.
Anja Almen, who lives in the building, said she heard a commotion from the street just after 5am, around 15 minutes after the explosion.
'I went out on the balcony and I was shocked. There was smoke everywhere, from every stairwell,' she said by phone from a nearby church to which she and other tenants were evacuated.
'Fire trucks with ladders were pulling people from apartments.'
Rescue operation chief John Pile told AFP that while an investigation was needed 'an explosion in a housing area, or an explosion in general, is not usually from natural causes.'
Sahlgrenska University Hospital, Gothenburg's largest, took in 16 people with injuries related to the blast and subsequent fire, press officer Ingrid Fredriksson said.
'But it's not certain there won't be more, as this is an ongoing event,' she told AFP.
Four of the people, three women and one man, were seriously injured, Fredriksson added.
Theodor Öréus, 24, who recently moved in, described how the shockwave reverberated all the way up to his apartment on the fifth floor.
'The front door of the apartment was slammed shut by the wave of pressure and smoke billowed into the apartment,' he told newspaper Aftonbladet.
Smoke billows from the rooftop of the block of flats in downtown Gothenburg on Tuesday morning
Firefighters at the scene stand beside glass windows on the ground floor from which smoke billows
'Because the stairwell was full of smoke, we couldn't get out. Instead, we had to go onto the balcony and climb over to the flat next door.'
'When we came down to the courtyard, people were fainting on the ground. Some have been picked up by ambulance,' Mr Öréus added.
Evacuees, some wearing only their dressing gowns, are being cared for across different sites, including the Saron Church nearby the the apartment block.
Around 40 have gone to the church, several of them are in shock, according to local social services official Ulla-Carin Moberg.
'We have blankets, coffee, coffee, and clothes. Some have not even brought any clothes with them,' Ms Moberg told Aftonbladet.
Many injured have been taken to Mölndal Hospital, which is part of Sahlgrenska University Hospital.
'At the hospital we have also set up a room for crisis support where people who have lost their homes can talk and get practical help,' Ms Moberg added.
Sweden has for years struggled to counter a rise in crime tied to gangs, with a spike in fatal shootings and bombings in an otherwise peaceful country.
In 2020, police recorded 107 detonations in the country of 10.3 million inhabitants, with another 102 recorded incidents involving attempted blasts or preparations.