Prosecutors in Belgium say 10 people have been arrested in three European countries on suspicion of planning to carry out an attack in Belgium.
The detainees are of Belgian, Dutch, Moroccan and Russian nationality.
Seven suspects were arrested in Belgium, two in the Netherlands and one in Germany.
Reports say some of the suspects are believed to be recruiters for a Chechen extremist group. They were detained after a year-long investigation by police in the Belgian city of Antwerp.
Police in Brussels also made several arrests in unrelated anti-terror raids. The detainees were due to appear before a specialist anti-terrorism judge in Antwerp.
In Germany, police said they had picked up a man near the city of Aachen in connection with suspicion of recruiting young men in Belgium to fight in Chechnya.
In the course of the Belgian investigation, other people were also arrested in Spain, Morocco and Saudi Arabia.
Germany warned last week it had strong evidence Islamic militants were planning attacks in the next two weeks and ordered security at its train stations, airports and other potential targets to be tightened.
But a spokesperson for the Ministry of the Interior says the latest
arrests are not connected to that security alert.