The former officials of Catalonia's government, including Carles Puigdemont, are now in Belgian capital.
Puigdemont and other sacked of the Spain's regional government will make a declaration of Catalonia soon, reports Reuters quoting newspaper La Vanguardia on Monday.
Other Barcelona-based paper El Periodico also said Puigdemont was in the Belgian capital, without giving any further detail.
Meanwhile, BBC reports, Spain government has brought several charges, including sedition and provocation, against Catalan leaders following the region's declaration of independence by regional parliament.
The attorney-general of Spain José Manuel Maza also made the announcement on Monday.
Catalonia's leaders, are going to be charged with misuse of funds for holding an independence 'illegal' referendum in early October, Maza said.
The charge of rebellion carries a maximum sentence of 30 years in prison. Under the Spanish legal system, the request will be considered by a judge, according to global media report.
Another BBC report says Spain's central government is set to take control of Catalan institutions with Spanish officials expected to be put in place in the region's ministries on Monday.
Madrid has called for the Spanish constitutional court to revoke Catalonia's unilateral vote for independence.
About 200,000 civil servants are due to arrive on Monday, but it is not clear how many will stay away or refuse to follow instructions.
The former Catalan Sustainability Minister, Josep Rull, said he was continuing with his "scheduled agenda" and posted an image on Twitter showing him at his desk.
"I'm at the office carrying out the responsibilities that the people [of Catalonia] entrusted to us," he wrote.
However, Madrid has given Catalan ministers hours to pack up their belongings and leave their offices or Catalonia's regional police force, known as Mossos, will "act".
Mossos, whose chief was dismissed last week, are deployed in Sant Jaume square, near the government palace in the centre of Barcelona.