Police in Belgium have killed two men during a raid against an Islamist group that prosecutors say was about to launch a terror attack on a grand scale.
About ten raids were carried out in three cities including Brussels.
Investigators say some of the suspects have fought in the civil war in Syria.
Thierry Werts is the Belgian Federal Prosecutor's spokesman.
"The raids were carried out in the framework of an investigation bearing on an operational cell made up of people of whom some had come back from Syria. The investigation was able to establish that this group was about to commit terrorist attacks on a grand scale in Belgium, and imminently."
A third man was detained in the eastern city of Verviers, where police commandos ran into a hail of gunfire after trying to gain entry to an apartment.
That suspect and the two who were killed are all said to be citizens of Belgium.
The country has one of the biggest concentrations of European Islamists fighting in Syria.
They were suspected of planning attacks on Belgian police stations.
Security across Belgium has been tightened following the raids.
Federal Prosecutors' spokesman Eric Van Der Sypt.
"Given this current situation, the coordination team for the threat analysis has decided to increase the threat level to level three, on a scale of four, for the police forces across the whole of Belgium, and it stays on level two at certain places but with a particular attention."
Earlier, prosecutors said they had detained a man in southern Belgium suspected of supplying weaponry to Amedy Coulibaly, the gunman who killed four people at a Paris Jewish grocery after the Charlie Hebdo attack.
Last week's terror attacks in Paris heightened fears across Europe of young local Muslims returning radicalized from Syria.
