MADRID (Reuters) - Britain's decision to leave the European Union strengthens the case for Catalonia to be allowed to seek independence from Spain, the head of the region's government said on Friday.

Joining other leaders of nationalist movements in Europe in welcoming the result of Thursday's Brexit referendum, Carles Puigdemont said Britain's ability to leave the EU without the approval of its member states suggested Catalonia could claim independence without Madrid's consent.

"It demonstrates that it is perfectly possible to take a decision about sovereignty as all other countries do," Puigdemont said in a statement.

Sworn in as leader in January, Puigdemont has mapped out an 18-month transition towards independence that would see Catalan authorities approve a constitution and begin building the institutions needed for an independent state, such as an army and a central bank.

The region's secession campaign gained momentum in 2014 from an independence referendum in Scotland, where voters eventually opted to remain part of the United Kingdom.

Puigdemont sent a message of support to Scotland, whose first minister Nicola Sturgeon said on Friday a second Scottish independence referendum was "highly likely."

In Thursday's plebiscite, a majority of Scots voted to stay in the EU.

Spain's acting Prime Minister Mariano Rajoy said Brexit demonstrated the risks of referendums and the divisions they gave rise to.

Rajoy, who faces a national election on Sunday, repeated he would never allow an independence referendum in a Spanish region. He has steadfastly opposed Catalan independence and refused to allow a referendum there in 2014, arguing it would contravene the constitution.

Beyond Catalonia, the historic British vote has fired up populist eurosceptic parties across the continent. Right-wing and anti-immigrant parties in the Netherlands, Denmark, Sweden and France have said they too should be allowed to hold referendums to decide national issues.

The separatist movement in Catalonia, which accounts for almost a fifth of Spanish economic output and has its own language, surged during Spain's economic crisis when it drew 1 million people onto the streets of Barcelona.

(Reporting by Angus Berwick; Editing by Julien Toyer and John Stonestreet)