Belgium's Foreign Minister Sophie Wilmes announced Thursday she was temporarily stepping down to support her husband in his battle against an aggressive brain cancer.

Wilmes, 47, who has been in her post since October 2020 after spending a year as prime minister, said she needed to provide "help and comfort" to her husband Christopher Stone and their three children.

Prime Minister Alexander De Croo will cover her portfolio.

"Unfortunately, life sometimes takes painful turns," Wilmes said, in a letter posted on Twitter.

"Illness has suddenly entered our lives and, in particular, that of my husband, Christopher, who must begin -- like far too many men, women and even children -- his fight against an aggressive brain cancer."

Stone, 63, is an Australian businessman and former Australian rules footballer who played for Melbourne side St Kilda between 1978 and 1981.

Wilmes said the "total commitment" required by her job "would not allow me to provide the help and comfort that Christopher and our children will need during this difficult time".

She said she had immediately put herself on unpaid leave from her ministerial duties.

"This gives us the ability to fully consider our situation by the end of the summer," said Wilmes.

In a separate statement, De Croo announced that he would temporarily take over the foreign and European affairs brief.

He said Wilmes would officially remain a member of the government.

In addition to his presence at heads of state and government summits, De Croo will therefore represent Belgium at European Union and NATO foreign ministers' meetings.

The portfolio has grown increasingly important since the outbreak of Russia's war in Ukraine.

"I wish Sophie, Chris and their children much courage and strength," De Croo said.

Wilmes, Belgium's budget minister from 2015 to 2019, became the kingdom's first woman prime minister following the departure of PM Charles Michel -- also from the French-speaking liberal party Reformist Movement -- to become the European Council president.

She spent a year as PM before the installation of a majority coalition of seven parties led by De Croo of the Flemish liberals Open VLD.

As premier, Wilmes had to handle the first wave of the Covid-19 pandemic in early 2020, when Belgium had a particularly high death rate.

Her communication skills and empathy were generally praised in the media.

Small business minister David Clarinval will take over Wilmes's additional duties in foreign trade, while digitalisation junior minister Mathieu Michel will cover her federal cultural institutions role.