Story highlights Two suicide bombers entered Europe at the same entry point in Greece on the same day

Hasna Ait Boulahcen did not blow herself up in raid; rather, a man detonated a suicide device

Third body found in wake of Saint-Denis raid

(CNN) Citing a "serious and imminent threat," Belgium has placed Brussels at the highest terror alert level.

The Crisis Centre of the Belgian Interior Minister said the terror alert level for the Brussels area will rise to level 4, which means very serious, while the rest of the country will remain at level 3. Residents are urged to avoid "places with high concentrations of people" such as concerts, train stations and airports.

The increase in alert level for Brussels comes as authorities investigating last week's attacks in Paris conduct raids in Belgium as they work to take down the network of terrorists behind the carnage.

Salah Abdeslam, 26, is the subject of an international search warrant. He was last seen driving toward the Belgian border, when police stopped and questioned him a few hours after the attacks, not knowing he was involved. Now, his whereabouts are unknown.

Here are the most important developments: