Belgian police on Thursday detained six more people over an alleged New Year attack plot in Brussels and arrested a 10th suspect over last month's jihadist massacre in Paris.
Both Brussels and Paris have cancelled annual New Year's Eve fireworks displays as soldiers and police ramped up security not only in those and other European capitals but also in the Turkish capital Ankara over perceived terror threats.
"It's better not to take any risks," Brussels Mayor Yvan Mayeur said when he announced the showpiece event's cancellation late Wednesday.
Officials said two men, Said S. and Mohammed K., had already been formally charged with terrorism-related offences and police detained six more people on Thursday for questioning over an alleged plot to strike "emblematic sites" in the Belgian capital during the end-of-year festivities.
A source close to the investigation told AFP that officials were trying to determine whether members of a motorcyle gang called the "Kamikaze Riders" were involved.
Six other people were detained following seven police raids in and around the Belgian capital in which computer equipment, mobile phones and "airsoft material" were seized, it added. Airsoft is a type of airgun.
'Terrorist murder'
Brussels has been on high alert since it emerged that several of the attackers involved in the Paris carnage on November 13 had links to the Belgian capital.
Prosecutors said on Thursday they have arrested a 10th suspect over the jihadist attacks in Paris that killed 130 people and wounded hundreds more. They charged him with terror offences.
The Belgian national, identified only as Ayoub B., was detained on Wednesday during a raid on a house in the troubled Brussels immigrant neighbourhood of Molenbeek, a statement from the federal prosecutor's office said.
He has been charged with "terrorist murder" and involvement in the activities of a terrorist group, it said, adding that he will appear in court again within five days for a custody hearing.
Molenbeek is home to the Paris attacks fugitive Salah Abdeslam and has emerged as a European hotbed of Islamist extremism.
Mayeur said on Wednesday that fireworks and related events in the central square of Place de Brouckere had been cancelled because it was not possible to "guarantee that we can check everyone coming to the event" in the current circumstances.
Last year, some 100,000 people turned out to watch the traditional New Year's Eve fireworks display.
'Delicate decision'
Speaking for the first time since the attack plot was revealed, Belgian Prime Minister Charles Michel said the decision to cancel the festivities was a tough one but the right one.
"It was, I understand, a delicate, difficult decision for the mayor to take," Michel said.
It is not however the first time the New Year's Eve fireworks have been cancelled as the authorities made the same decision in 2007 because of another terror threat.
Officials said the plot revealed Tuesday was not directly linked to the wave of bombings and shootings on a Paris concert venue, bars, restaurants and the national stadium.
The fugitive suspect Abdeslam is believed to have fled to Brussels in the hours after the attacks claimed by the Islamic State jihadist group.
In Turkey, meanwhile, officials said two Islamic State suspects, reportedly both Turks, were planning to stage suicide bombings in the centre of the capital Ankara, which is expected to be packed with revellers on the night of December 31.
Turkey has been on high security alert since October, when two suicide bombers blew themselves up in a crowd of peace activists in Ankara, killing 103 people in the worst attack in the country's modern history.
Moscow's Red Square, traditionally a place where people gather to ring in the New Year, will be closed to revellers on December 31 while Vienna has also beefed up security ahead of the celebrations.
The French capital also remains on high alert and has abandoned its fireworks display on the Champs-Elysees, although the traditional gathering on the famous boulevard will go ahead under tight security.