The move comes after Belgium's asylum and migration affairs minister Theo Francken said the former president could seek asylum in the country.
The Spanish media reports that the former leader is accompanied by an unspecified number of other members of the Catalan government.
The group are expected to make a joint statement later today.
Spain's prosecutor José Manuel Maza said on Monday morning that rebellion, sedition, and provocation charges would be levelled at the former leaders of the Catalan government, which has been suspended by the Spanish central government in Madrid.
In accordance with Spanish law a judge will not assess the charges.
Spain has refused to recognise the result of an independence referendum held by Catalonia's regional government at the start of the month on the basis that it is illegal under Spanish law.
After the Catalan regional parliament voted to declare independence on Friday, the Spanish government said it would revoke the region's autonomy and rule it directly from Madrid.
Belgian asylum minister Mr Francken hails from the Flemish nationalist party New Flemish Alliance, which has close ties to the Catalan separatist movement.
His party advocates an independent Flanders and wants it to secede from Belgium.
“Catalan people who feel politically threatened can ask for asylum in Belgium. That includes President Puigdemont. This is 100 percent legal,” Mr Francken told Belgian public broadcaster VRT at the weekend.
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