French President Francois Hollande expressed France's solidarity in the aftermath of the explosions at Brussels airport and Metro system, which have killed multiple people and injured dozens more today (22 March 2016).

"Cowardly and horrible attacks were perpetrated, resulting in numerous deaths, and dozens of injured. I would like to express my solidarity and friendship towards the Belgian people and authorities, who are dealing with a lot, and say to the families concerned that all our thoughts are with them, sharing their pain," Hollande told a news conference.

The blasts at the airport and Metro station occurred four days after the arrest of Salah Abdeslam in Brussels, a suspected participant in the November attacks in Paris that killed 130 people.

Brussels explosions LIVE UPDATES: 13 dead after blasts at Zaventem airport and Maalbeek Metro

"Terrorism has hit Belgium, but Europe was targeted, and the whole world is concerned. We need to realize the extent and gravity of this terrorist threat. These attacks follow others – Paris was particularly targeted last year," Hollande said.

Security services have been on a high state of alert across western Europe for fear of militant attacks backed by Islamic State (Isis), which claimed responsibility for the Paris attacks. Hollande reiterated that the threat of radical militant groups must be met with a global response.

"We are facing a global threat, which demands a global response. France and Belgium are connected, connected by horror. We once again share it. And I expressed to the Belgian government our vital support, so we can bring them all the means necessary," he said.

Britain, Germany, France and the Netherlands, all wary of spillover from conflict in Syria, were among states announcing extra security measures in the wake of the attacks in Belgium. All public transport in Brussels was shut down, as it was in London during 2005 Islamist militant attacks there that killed 52 people.