Multiple explosions took place on Tuesday at the Brussels airport in Belgium. The cause of the explosions is not yet known.
Airport spokeswoman Anke Fransen said, "There were two blasts in the departure hall. First aid team are in place for help."
Images on the website of public broadcaster RTBF showed smoke rising from the terminal building, where the windows had been shattered, reported AFP.
The broadcaster said the blasts hit shortly after 7.00 am (GMT) and that regional authorities had gone into emergency mode, with all flights in and out of the airport halted.
There was no immediate confirmation of the cause of the blasts or of any injuries, but RTBF cited a witness who said they had seen several wounded people.
Belgian news agency Belga said shots were fired and there were shouts in Arabic shortly before the explosions, reported Reuters.
Interior Minister Jan Jambon announced that Belgium's terror threat had been raised to its highest level.
Images also showed people fleeing from the terminal building.
Reports said that one of the explosions took place near the American Airlines check-in desk. Several people have been injured after the blasts, although the number of people injured is still unknown.
Train services to the Brussels airport have also been suspended and there is a complete lockdown at the airport.
The entire area has been cordoned off, all flights from the airport have been grounded and the airport is being evacuated.
Passengers were led onto the tarmac and the crisis centre urged people not to come to the airport.
Belgium closed metro, train, tram and bus services in Brussels following bomb blasts in the airport and metro, the authorities said.
"Bus, tram and metro shut down," the Brussels public transport operator STIB said in a message on Twitter. Major railway stations are also closed, the Brussels public prosecutor said separately.
Meanwhile, the Twitter handle of Brussels Airport tweeted out the following message: "There have been 2 explosions at the airport. Building is being evacuated. Don't come to the airport area. Airport is being evacuated. Avoid the airport area. Flights have been cancelled. All airport operations have been suspended until further notice. Follow the information on our website. Passengers that are still located in other area's in the airport are asked to remain calm and wait for further information."
A passenger of Indian origin told Times Now, "We were at the airport after the flight from Mumbai to Brussels landed at the airport. We heard huge explosions. We didn't realise what had happened. Everyone is in shock. So we don't know what is happening."
The explosions in Brussels are "an attack against democratic Europe," Swedish Prime Minister Stefan Lofven said.
"It is an attack against democratic Europe. We will never accept that terrorists attack our open societies," he told news agency TT in a statement, while his Danish counterpart Lars Lokke Rasmussen denounced the blasts on Twitter as a "despicable attack".
Europe's main stock markets retreated as the news broke, with London's benchmark FTSE 100 index dropping 0.6 percent compared with Monday's close and Frankfurt's DAX 30 shedding 1.1 percent.
Mike van Dulken, head of research at Accendo Markets, said that the "explosion at Brussels airport... has knocked sentiment".
The explosions happened only days after the prime suspect in the Paris attacks Salah Abdeslam was arrested in Brussels.
(With agency inputs)