Brussels terror attack A timeline

Brussels: Brussels, home of the European Union (EU) and NATO, was hit Tuesday by bomb attacks at the airport and in the metro that killed around 35 people.

Authorities say some of those responsible for the carnage might still be at large and have asked media not to report on details of the ongoing investigation. The blasts occurred four days after the arrest of Salah Abdeslam, the prime suspect in the Paris terror attacks claimed by the Islamic State group.

Here is a timeline of what has happened so far on Tuesday.

Around 0700 GMT (8:00 a.m. local time): Two blasts hit Zaventem international airport outside Brussels. Witnesses cited by the Belga news agency say they first heard shots in the departure hall before someone shouted in Arabic and then two explosions occurred.

Shortly before 0800 GMT: Federal police say at least one person is dead and several others wounded.

The airport is closed and a crisis cell meets at the interior ministry.

Shortly after 0800 GMT: A third explosion rocks the Maalbeek metro station near the EU headquarters. Around a dozen injuries are reported at first.

0815 GMT: Belgium moves to its highest level of terror alert.

Shortly before 0900 GMT: The European Commission tells staff to stay home or in their offices.

Shortly after 0900 GMT:  The federal prosecutor's office issues a casualty toll of at least 13 dead and 35 wounded at the airport.

Shortly before 0930 GMT: The crisis centre asks inhabitants to stay put, and all public transport systems grind to a halt.

Security is reinforced in airports, train stations and public transport systems in Paris, while airports in Frankfurt, London, Moscow and the Netherlands beef up their measures too. The border between Belgium and the Netherlands is reinforced.

Shortly before 1000 GMT: Fire services say at least 21 people have died, including 11 at the airport.

High-speed Thalys trains between Belgium, France and the Netherlands stop running.

1015 GMT: European Council President Donald Tusk condemns the "terrorist attacks".

Shortly before 1030 GMT, police and soldiers reinforce security around Belgium's nuclear power plants.

1043 GMT: Belgian Prime Minister Charles Michel condemns the "blind, violent and cowardly" attacks.

1046 GMT: Paris Mayor Anne Hidalgo says the Eiffel Tower will be lit in Belgium's national colours and calls for a silent vigil in the evening in Paris.

Shortly before 1100 GMT: Federal prosecutor Frederic Van Leeuw says one airport blast was "probably caused by a suicide bomber."

1100 GMT: "The whole of Europe has been hit," says French President Francois Hollande.

1115 GMT: Brussels transport operator STIB says the metro blast killed at least 15 people and wounded at least 55, including 30 seriously.

Eurostar train service between London and Brussels is suspended.

1230 GMT: "We will never let these terrorists win," says British Prime Minister David Cameron.

1235 GMT: The investigation is ongoing and authorities "fear that people are still at large," says Belgian Foreign Minister Didier Reynders.

1336 GMT: Local mayor Yvan Mayeur says "there are around 20 dead with another 106 wounded, 17 of them gravely" at the metro station.

1357 GMT: A fire service spokesman says the airport attack killed 14 people and left more than 90 wounded, and warns the toll could change.

The number of known casualties stands at around 35 dead and more than 200 wounded.