At least one person has died after two explosions in the departure hall of the main airport in the Belgian capital Brussels on Tuesday, local media report.
Another explosion also took place in the Brussels subway station Maalbeek, which is located near the seat of EU institutions, the RTBF broadcaster reports.
The Belga news agency quoted unnamed sources as saying that a blast had occurred too at the Schuman subway station, which is adjacent to the European Commission.
The Brussels subway is being shut down, the STIB subway operator wrote on Twitter.
Belgium has raised its terror alert level to 4, which indicates a "serious and imminent" threat, local media reported.
At the Brussels airport, several people were said to be injured.
"There have been two explosions at the airport. Building is being evacuated. Don't come to the airport area," Brussels Airport wrote on its Twitter account. "Flights have been cancelled."
Train traffic to the airport has also been halted, the SNCB rail company wrote on Twitter.
Pictures posted on social media showed a blown-out window front, debris that appeared to come from a collapsed roof and bloodied people inside and outside the airport. Smoke could also been seen rising from the building.
The explosions at the airport took place one after the other around 8 am (0700 GMT), eyewitnesses told the Belga news agency. Eyewitnesses told the news agency that they had heard shots and calls in Arabic before the explosions.
It was not immediately clear if the incident was a terrorist attack, the broadcaster RTBF reported.
Belgium had been on high alert since the arrest in Brussels last week of Salah Abdeslam, a key suspect in the Paris terrorist attacks.