Brussels on Lockdown After 'Serious and Imminent Threat' of Terror Attack

With Belgium's capital on lockdown over a "serious and imminent" threat of a terror attack, Turkish authorities reportedly arrested a Belgian national involved in plotting the coordinated assault on Paris a week ago.

A Turkish government official said on Saturday that authorities detained Ahmet Dahmani, a 26-year-old Belgian of Moroccan origin, at a luxury hotel in the southern coastal city of Antalya. Turkey's Dogan news agency quoted the unnamed official as saying Dahmani is suspected of scouting target sites for the Paris attacks. Two other men, both Syrian, were detained on suspicion of planning to help him cross safely into Syria. Dahmani reportedly traveled to Turkey from Amsterdam on November 14.

The Turkish official said Belgian authorities failed to alert Turkey about Dahmani. "Had the Belgian authorities alerted us in due time, Dahmani could have been apprehended at the airport" the official reportedly said. Dahmani's name was not included on the roster of more than 26,000 people banned from entering Turkey.

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On Friday night, the Crisis Center of the Belgian Interior Ministry placed Brussels on the country's highest level "four" alert after a meeting of police, justice, and intelligence officials. At a press conference on Saturday, Michel said the alert was raised because "relatively precise information pointed to the risk of an attack along the lines of what took place in Paris." Michel says people should be alert but not panic, and stay inside or avoid public places or events such as concert halls, shopping centers, sports arenas, and transportation hubs.

We are at a police operation in Brussels suburb, police telling us to stay back. — Keir Simmons (@KeirSimmons)November 16, 2015

"We are talking about the threat that several individuals with arms and explosives would launch an attack" Michel said. "Perhaps in several locations at the same time."

In the aftermath of the attacks on Paris, attention turned to the failings of Belgian security to identify some of its extremist cells or "hotbeds of radicalization" before it was too late.

French President Francois Hollande said that the coordinated assault on France's capital was planned in Belgium. In response, Belgian Prime Minister Charles Michel said on Thursday that the country would start jailing returning jihadists from Syria and shutter unregistered mosques. Michel also pledged to spend an additional 400 million euros on security measures to fight extremism.

Abdelhamid Abaaoud, a Belgian national and the suspected architect of the Paris attacks, was killed on Wednesday during a police raid north of Paris. Salah Abdeslam, also suspected to be a key conspirator, is still at large. Authorities believe that Abdeslam, also a Belgian national, drove a getaway car and crossed the border hours after the attacks on Paris in which his brother Brahim blew himself up in a suicide bombing. Abaaoud and Abdeslam both grew up in the Molenbeek district of Brussels.

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"With the conflicts in Syria and Iraq in particular, there has been a radicalization that we have never seen before," Molenbeek mayor Francoise Shepman said on the Monday following the attacks on Paris.

"I see there is nearly always a Molenbeek link," Michel said, referring to the Paris attackers, the attack on Charlie Hebdo magazine in January, and the attack on the Jewish museum in Brussels last year. Many of the assailants were found to have ties to Belgium, and more specifically, Molenbeek. "There is a gigantic problem," Michel said.

The terror alert means that the Brussels metro system will remain closed until Sunday. Some tram stations have also stopped operating, and military personnel have been stationed across the city outside entrances of hotels. Restaurants and cafes have reportedly been asked to close by 6pm local time.

Michel says that the threat level would be reassessed on Sunday. The US Embassy has urged Americans to "shelter in place." Interior Minister Jan Jambon said that there is no specific threat directed toward European Union institutions, which are located in Brussels.

Follow Tess Owen on Twitter: @misstessowen

Reuters contributed to this report.