FILE PHOTO: Belgium's Prime Minister Charles Michel attends a joint news conference with French President Emmanuel Macron, Luxembourg's Prime Minister Xavier Bettel and Netherlands' Prime Minister Mark Rutte at Bourglinster castle in Luxembourg September 6, 2018. REUTERS/Francois Lenoir

BRUSSELS (Reuters) - The liberal party of Belgian Prime Minister Charles Michel lost ground in local elections, throwing into doubt whether he will be able to continue his center-right coalition after a national vote next year.

Belgium will hold federal and regional elections on May 26, the same day as elections held across the European Union for seats in the European Parliament.

In Sunday’s regional elections, Michel’s Mouvement Reformateur (MR) slipped by around 4 percentage points in all but one of the provinces in Wallonia, the French-speaking southern region of Belgium, and lost a number of mayoral posts in the capital Brussels.

Michel told broadcaster RTBF that his party had done better than forecast by opinion polls.

“We are relatively stable,” he said.

In the Dutch-speaking north of the country, Flanders, the three parties ruling at national level had mixed results. Bart De Wever, the leader of the separatist N-VA, was on course to stay on as mayor of Belgium’s second city, Antwerp.

Federal governments in Belgium result from separate elections in Flanders and Wallonia. Michel’s government, in power since 2014, is unusual in that it contains only one French-speaking party and lacks a majority in the south of the country.

The local election’s big winners, north and south, were the Greens, with gains also registered by the hard left PTB in Wallonia and the separatist anti-immigrant Vlaams Belang in Flanders.