Image copyright AP Image caption Firefighters said they suspected the fire was started by sparks from underground welding work

Seven people have been killed and 20 others injured in a fire at a bus terminal in South Korea, officials say.

The fire occurred on Monday morning in Goyang city, northwest of the capital city, Seoul.

Firefighters believe welding works at an underground construction site in the building started the blaze, which was brought under control in 20 minutes.

The incident left two people in critical condition, emergency officials said.

Several people suffered smoke inhalation and were taken to hospital for treatment, said the BBC's Lucy Williamson in Seoul.

Image copyright AP Image caption This photo taken by a Goyang resident shows smoke rising from the bus terminal

Bodies were found at the basement construction site, Yonhap news agency reported.

The incident has come at a time of grief and national mourning as South Korea struggles to recover from a ferry sinking in April that left more than 300 people dead or missing.

South Korean President Park Geun-hye has formally apologised to the nation for the disaster, promising to improve safety standards.

Two subway cars also collided in Seoul in early May, injuring dozens of people.