During one search, 26-thousand euro was seized but no weapons or explosives have been found.
The suspect Salah Abdeslam – who's been the subject of a major manhunt since the Paris attacks – is not among those arrested.
Irish Times Correspondent in Brussels Suzanne Lynch says the city remains in lockdown.
David Cameron's agreed to strengthen counter-terrorism ties between the UK and France.
He's offered the French air force the use of the RAF's base in Cyprus – after president Francois Hollande confirmed he'd be intensifying air strikes against Islamic State in Syria.
The British Prime Minister's repeated his conviction that the UK should also be involved – and says he'll be making a statement about that to Parliament later this week.
Meanwhile, those with a radical interpretation of Islam should not be allowed to come to Ireland to communicate with the Muslim community.
That's according to the Imam of the Al-Mustafa Islamic Centre in Dublin.
He says that Islamic radicals are not necessarily here to recruit terrorist fighters – but they shouldn't be allowed to preach to the Muslim community in Ireland.
Shaykh Dr. Muhammad Umar Al-Qadri says that many speakers have come to Ireland with radical views.
