Belgian lawyer Paul Bekaert confirmed Carles Puigdemont was in Brussels and would make a public appearance in the city on Tuesday.
After a meeting in his office in western Belgium, Bekaert said his client was in high spirits, driven by "strong support among his backers in Catalonia".
On the first working day since his regional government was sacked, Mr Puigdemont and other Catalan leaders were accused of committing offences which carry sentences of up to 30, 15 and six years in prison respectively.
Hours later, Puigdemont and five former members of his cabinet reportedly drove to Marseille, where they boarded a flight to the Belgian capital.
The development sparked rumours Mr Puigdemont would seek political asylum in Brussels - a prospect that Belgian migration minister Theo Francken described as "not unrealistic" and "100% legal".
However, Belgian Prime Minister Charles Michel appeared to dampen that suggestion. He asked Mr Francken "not to fan the flames", adding an asylum request was "absolutely not on the agenda".
Bekaert said: "Puigdemont is not in Belgium to request asylum", only to prepare a legal riposte to any eventual moves by Madrid.
"On this matter (asylum) nothing has yet been decided," he told Flemish television VRT.
"I'm his lawyer in case he needs me," Mr Bekaert said. "At the moment there are no specific dossiers I am preparing for him."
Earlier, officials confirmed Catalonia's parliament had been dissolved and that its speaker would only lead a transitional committee until regional elections are held on 21 December.
Pro-independence MP Josep Rull defied Madrid's orders by turning up to work at Catalonia's parliament and was warned by police to pack up his desk or risk being arrested.
Tweeting a picture of himself at his desk, Rull said: "In the office, exercising the responsibilities entrusted to us by the people of Catalonia."
Meanwhile, Puigdemont fuelled speculation he had already arrived at work by posting a picture of what appeared to be the presidential palace.
Spanish attorney general Jose Manuel Maza said the disputed president and other Catalan leaders had "caused an institutional crisis" by voting to declare independence from Spain on Friday.
