Brussels - Belgian police arrested several suspects in Brussels on Saturday during raids connected to the Paris attacks, including one who was in the French capital at the time of the carnage, officials said.
The arrests - local media said three people were detained - were in connection with a vehicle found near the Bataclan concert hall where the majority of the 129 victims were killed, they said.
The arrests were in the poor Brussels district of Molenbeek, which has been linked to several other past terror plots amid concerns Belgium has become a hotbed of European militancy.
Prime Minister Charles Michel said there had been "several" arrests and told RTBF television: "It is believed or suspected that one of these people was in Paris last night." Belgian Justice Minister Koen Geens said separately that the arrests in Molenbeek "can be seen in connection with a grey Polo car rented in Belgium" found near the Bataclan.
"The person who rented the car was Belgian. We know this from his brother," said Geens, adding the brother had been arrested.
Parking tickets from Molenbeek were found inside the car with Belgian license plates, Belgian media said. In Paris, several witness reported that some of the attackers arrived in a vehicle with Belgian licence plates.
Separately the Paris prosecutor, Francois Molins, said one of the vehicles used in Friday's attacks in the French capital was registered in Belgium and hired by a French national living there.
That Frenchman and two others travelling with him were arrested by Belgian police during a traffic stop in another vehicle, the prosecutor said in Paris, adding that they were not known to French intelligence.
The Belgian federal prosecutor meanwhile said authorities had now opened a formal terrorism investigation.
Footage on Belgian television showed plainclothes officers pointing automatic pistols at a man on his knees, while a uniformed police officer carrying a sub-machinegun warned onlookers to stay away.
"An old model Golf was stopped as it was driving. The police made the man get out and they shoved him in the back, made him kneel and then put a blindfold on him," a resident told AFP on condition of anonymity.
"The man was between 30 and 40. He was dressed normally in jeans and a hoodie. He wasn't bearded, he looked normal," the witness added.
Belgium has the highest per-capita number of nationals who have travelled to fight with the Islamic State in Syria and Iraq, officials and analysts have said.
In January, just days after the Charlie Hebdo attacks in Paris, two suspected militants were shot dead in a police raid in the eastern Belgian city of Verviers.
Police later said they had smashed a cell aiming to kill police officers. The alleged mastermind of that plot - Abdelhamid Abaaoud - was from Molenbeek.
Investigators said they also suspected a Belgian man could have supplied Amedy Coulibaly, the gunman behind a Jewish supermarket attack also in Paris in January, with his weapons.
Meanwhile the man behind August's foiled attack on an Amsterdam-Paris train, Ayoub El Khazzani, had stayed with his sister in Molenbeek before getting the train.