At least five people were killed Saturday and 27 were injured when a freight train transporting gas derailed and exploded in the northeastern Bulgarian village of Hitrino, officials said.

"Five victims have been confirmed dead so far and 27 injured," the interior ministry said in a statement.

The train was carrying more than 20 tankers of propylene gas and propane butane when it derailed while entering the village's rail station.

The last two tankers hit a power line and exploded and seven tankers full of propylene went off the tracks, local police spokeswoman Assia Yordannova said.

The blast occurred at 5:37am (0337 GMT) at the village, located about 100 kilometres (60 miles) from Varna, Bulgaria's main port on the Black Sea.

The interior ministry said there were 200 firefighters and rescuers at the scene. More than 50 houses were damaged and 40 families evacuated.

"Four victims have been identified but we fear there will be more. Twenty-five people were injured," civil defence chief Nikolay Nikolov said.

A hospital in the nearby town of Shumen said an 18-year-old man had died from his injuries, while three people with life-threatening burns have been transported to a hospital in the city of Varna, Bulgaria's largest port on the Black Sea.

Aerial footage showed a massive plume of black smoke rising over the small village, which is home to some 800 people.

Charred tankers lay scattered around the tracks of the nearly ruined railway station. There was debris everywhere.

"There is devastation in the area around the blast site. Twelve people have been rescued from under the ruins alive so far and firefighters are checking for more," Nikolov added.

Hitrino's station, the police headquarters and several homes along the railway tracks were razed.

Fires raging in the area were put out around noon, local authorities said.

"There will be more than five victims. There are several injured with 90 percent burns," Bulgaria's outgoing Prime Minister Boyko Borisov after arriving at the site. He appealed for blood donations for the hospitals treating the injuries.

Residents said the firefighters had been "very slow" to arrive and many burst into tears while recounting how their houses collapsed.

Cargo train accidents are relatively frequent in Bulgaria where railway tracks are obsolete and regularly pillaged by thiefs. But victims are extremely rare.