Arrests were reported in Belgium, Germany and France today following Tuesday's attacks in Brussels that killed more than 30 people.
It was confirmed today that a Briton, David Dixon, 53 - who was from Nottingham but lived in Brussels – was among those killed in the attack.
In a statement, the Foreign Office said: "We can confirm David Dixon lost his life in the attacks which took place in Brussels on Tuesday 22 March 2016.
"Our thoughts are with his family at this difficult time and our embassy staff are continuing to support them."
Prime Minister David Cameron tweeted: “I am deeply saddened to hear David Dixon was killed in the Brussels attacks. My thoughts and prayers are with his friends and family.”
Meanwhile, US secretary of state John Kerry arrived in Brussels today to offer assistance in security.
He said: "The United States is praying and grieving with you for the loved ones of those cruelly taken from us, including Americans, and for the many who were injured in these despicable attacks.”
The Belgian media are reporting there have been nine arrests made in the country in relation to the attacks earlier this week. Arrests in relation to the attacks have also been reported in France and Germany.