A vehicle drove at high speed into a group of Belgian carnival performers who were preparing a parade early on Sunday, killing four people and badly injuring seven others, Belgian media said.
Those in the vehicle, which local media said was a car, were detained. The cause of the incident was not immediately known. Police could not immediately be reached for comment. A news conference was set for 1000 GMT, state broadcaster RTBF said.
The incident occurred in the southern Belgium village of Strepy-Bracquegnies at around 0400 GMT, RTBF said.
Reuters, quoting news site Bel RTL, reports Jacques Gobert, mayor of the neighbouring town of La Louviere, as saying around 150 people were gathered to get ready for the annual folklore parade, involving costumes and drums, when the vehicle appeared.
"We heard an immense noise...and the car literally went into the group of people," said Bel RTL reporter Fabrice Collignon, who witnessed the event.
"A speeding car drove into the crowd...The driver then continued on his way, but we intercepted him," said Gobert.
Belgium has sought to root out people suspected of militant links over the past seven years. A Brussels-based Islamic State cell was involved in attacks on Paris in 2015 that killed 130 people and on Brussels in 2016 in which 32 died.
RTBF quoted local authorities as saying 15 also suffered light injuries in the incident.
