Belgian police arrested 16 people in 22 terror raids in the country today, including some in the Molenbeek neighborhood of Brussels, where officials say some of the suspects in the Paris attacks lived, but the fugitive sought in the attacks wasn't located.
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The federal prosecutor said the raids would continue into the night, as the search for alleged attacker Salah Abdeslam, who authorities said left Paris after the attacks and returned to his hometown in the Brussels area, goes on.
The raids came with the Belgian capital on high alert for a second straight day.
Earlier today, police cordoned off several streets around the Grand Place square in Brussels. Tense cops and soldiers hurried to set up roadblocks and barriers and to move people off the streets and sidewalks, as authorities say the city will remain on high alert at least overnight.
Some frantic police pointed guns and shouted as they tried to keep the streets clear.
The area that was cordoned off includes hotels and a police station. Guests of some hotels were advised, but not required, to stay inside.
Outside the cordoned off areas, people were able to move freely, but very few people were on the streets.
The significant lockdown lasted for about three to four hours before it started to be scaled back. While the heavy police and military presence remained, a few of the major streets were reopened to limited traffic and some side streets were reopened to foot traffic.
The police activity came just hours after Belgian Prime Minister Charles Michel said a terror threat level of 4 -- the highest level -- would remain in effect overnight for Brussels and the Brussels region, while level 3 would be maintained for the rest of the country.
He said the suspected possible targets included malls, shopping centers and public transportation.
The subway system in Brussels was to remain closed at least until Monday and Brussels' schools will be closed, the prime minister said. The country's crisis center urged people to steer clear of crowds.
The government raised the level Friday because of an "imminent" threat, Rudi Vervoort, Minister-President of Brussels, said on Belgian television network RTBF.
In its latest message, the U.S. Embassy in Brussels advised American citizens to remain at home and avoid public gatherings in response to the threat alert.
On Saturday, Vice Prime Minister Didier Reynders said Belgian authorities were looking for "one and more individuals with weapons, explosives."
"The threat is imminent, precise," Reynders said on Belgian television network RTL. "We're talking about possible attacks by several individuals, heavily armed, so obviously in parallel we are looking for one and more individuals with weapons, explosives."
Michel said Saturday there was a "threat of attacks with arms and explosives that could be launched in several locations at the same time." Michel added the decision to raise the alert level was made based on "rather precise" information.
Raids in Brussels followed the Paris attacks that killed 130 people last Friday.
Turkish authorities confirmed three suspected ISIS members were arrested Friday. Police say one of the suspects served as a lookout for the attacks at the Stade de France.
Aicha El-Hammar Castano, Rhonda Schwartz, Engin Bas in Istanbul, and The Associated Press contributed to this report.