Danes turned out on Thursday to wish their popular Queen Margrethe a happy 80th birthday, singing for her across the country at noon and waving red-and-white Danish flags, despite semi-confinement.

Grand festivities were cancelled due to the new coronavirus, but Danes of all ages stood on balconies, in the streets, in parks and their apartments to join in a song for the queen, respecting social distancing rules, in images broadcast live by Danish television DR.

The queen, dressed in a mint green skirt suit and her silver hair tied up in a chignon, watched on television, seated on a couch in her Fredensborg palace, north of Copenhagen, where she is self-isolating.

After several songs, the queen came out onto the palace steps and waved to the well-wishers, stood several metres apart. Margrethe has reigned for almost half a century, taking over on January 14, 1972 on the death of her father, King Frederik IX, when she was 31.

A 2018 Voxmeter survey found three-quarters of Danes support the monarchy, while only 14.6 percent would prefer a republic. Some 80 percent also said they felt they were well-represented by the queen and her two sons, Crown Prince Frederik, 51, and Prince Joachim, 50, and their families. Her French-born husband, Prince Consort Henrik, died in 2018.

A smoker, Margrethe is the first female regent in Europe's oldest monarchy, and has repeatedly insisted she will not abdicate. "I'll stay on the throne until I drop," she reiterates regularly.

Royal watchers attribute her popularity to an ability to unite the nation and serve as a moral authority, as well as her success at gradually modernising the monarchy.

She is also known for designing costumes and sets for the ballet and television, as well as her painting and book illustrations.

Denmark began reopening schools for younger children on Wednesday after a month-long closure to combat the COVID-19 pandemic, becoming the first country in Europe to do so.