Princess Charlene of Monaco has returned to the principality after months-long medical treatment abroad and will continue her recovery alongside her husband and children, according to her palace.

"In accordance with her doctors and while her recovery is going well, their royal highnesses have agreed together that Princess Charlene can now continue her convalescence in the principality with her husband and their children," a palace statement said yesterday.

It added that "the coming weeks should enable her to recover completely in order to be able to resume her official duties progressively".

The ex-swimmer, who married Prince Albert of Monaco in 2011, was admitted to a private Swiss clinic for treatment for "extreme fatigue" in late November, sources said at the time.

She is also thought to have undergone dental treatment.

"She was clearly exhausted, physically and emotionally. She was overwhelmed and couldn't face official duties, life in general or even family life," Albert told People magazine in November.

Zimbabwean-born Princess Charlene was hospitalised after collapsing in September in South Africa, where she had been living for several months.

The statement said that she still needed "calm and serenity".

The couple has been dogged by rumours about their rocky relationship almost since their marriage, which was briefly hailed as a fairy-tale match for a prince long described as the world's most eligible bachelor.

Her prolonged absence in South Africa last year sparked speculation in European celebrity magazines that the couple were headed for divorce.

She underwent surgery in October for an ear, nose and throat infection after checking in under a pseudonym in a Durban hospital, a palace source said at the time.

Albert is the son of Prince Rainier III and Grace Kelly, an American film star who died in a car accident in 1982.

Kelly's grandfather was born in Mayo in the 1850s and emigrated to the US in the 1880s.