At least 45 people – including 12 children – have been killed after a bus caught fire on a highway in western Bulgaria early on Tuesday.

A senior interior ministry official confirmed that children were among the dead and seven people – who had jumped out of the burning bus – had been taken to hospital for treatment in the Bulgarian capital, Sofia, with burns.

The incident happened on the Struma highway near the village of Bosnek, 28 miles (45km) west of Sofia, at around 2am local time and either the "bus caught fire and crashed, or crashed and then caught fire", Nikolai Nikolov said.

He said there were 45 fatalities. But the ministry later said there were 46 casualties, before giving a further update of one less than the toll given earlier.

The death toll was confirmed by Bulgaria’s national police chief Stanimir Stanev, who added 52 people were on board including the driver.

Most of the victims were tourists from North Macedonia, an official from the country’s embassy told BTV, where the bus was registered and the driver was from. It was one of four travelling together.

Albanian foreign minister Olta Xhacka said the passengers were from North Macedonia’s ethnic Albanian community.

They were on their way back to Skopje, the capital, after a weekend holiday trip to Istanbul in Turkey, said North Macedonian foreign minister Bujar Osman.

"People are clustered inside and are burnt to ash," said Bulgaria’s interior minister Boyko Rashkov.

"The picture is terrifying, terrifying. I have never seen anything like that before," he told reporters at the site.

The cause of the incident is unclear, but Bulgarian officials said the bus appeared to have struck a road barrier either before or after it caught fire.

Photos taken shortly after the crash showed the bus engulfed in flames with plumes of thick, black smoke.

Bulgarian investigative service chief Borislav Sarafov said either there had been a "human error by the driver or a technical malfunction".

Footage showed the burnt-out bus charred and gutted by the blaze in the middle of the road which was wet from rain.

It was surrounded by firefighters and emergency crews who had rushed to the scene which was sealed off with forensics officers on site.

"I am terrified. This is such a huge tragedy," North Macedonian Prime Minister Zoran Zaev told BTV.

The country’s president, Stevo Pendarovski, called it a "horrific accident" and said he expects the authorities to conduct a full investigation.

He said he had spoken to one of the survivors who told him passengers were sleeping when they were woken by the sound of an explosion.

Students at Ismail Qemali elementary school in Skopje were mourning the loss of five of their schoolfriends, according to Reuters news agency.

In Sofia, Adnan Yasharovski, 45, said his 16-year-old daughter Zuleikha called him to say she had survived the crash, and he had travelled to see her in hospital.

"She was crying. Her hands were burnt but otherwise fine," he said. "She didn’t say much, she was crying and she was in shock. I only saw her through the door as due to COVID, they did not let me into the room."

Mr Zaev added one person from Serbia and a Belgian national were among those travelling on the bus. It was unclear if they were among the victims or injured.

Representatives from Macedonia’s embassy visited the hospital where some of the victims were taken, according to Bulgarian news agency Novinite.

A hospital official said the survivors – two women and five men – receiving treatment were all in a stable condition, and one had a broken leg.

Bulgarian interim prime minister Stefan Yanev visited the crash site and described the incident as "a huge tragedy".

"I take this opportunity to send my condolences to the relatives of the victims," he said.

"Let’s hope we learn lessons from this tragic incident and we can prevent such incidents in the future."

© Sky News 2021