The blasts scene at Brussels Zaventem Airport. [Photo: cnr.cn]

BRUSSELS, March 22 -- All metro, tram and bus services have been shut down following explosions in the Brussels airport and the Maelbeek station close to the European Union institutions in the city center on Tuesday, the city's public transport operator STIB announced.

"Due to the events in Brussels, at the request of the police. No metro, tram or bus is operated," STIB announced on its official website.

A witness told Xinhua the metro train she boarded stopped halfway while heading from Arts-Loi to Maelbeek. She said there was a strong smell of burnt metal and people have to get out of the train and walk on the track towards Arts-Loi to get out. Outside, police vehicles were "everywhere," she said.

The witness told Xinhua she saw a body on the ground with a cover while walking past the Maelbeek station.

Reports have put the death toll in the explosions as high as 17.

The country's threat level has been raised from three to four, or the highest level.