Queen Elizabeth II on Monday met visiting Canadian Prime Minister Justin Trudeau, in her first in-person engagement since falling ill with Covid-19.

The 95-year-old monarch, who is also queen of Canada, chatted with Trudeau after he jetted in for talks on the conflict in Ukraine with UK Prime Minister Boris Johnson and Dutch counterpart Mark Rutte.

Last week the queen donated to an appeal for funds to help Ukrainian refugees, while her eldest son and heir, Prince Charles, called the invasion "an attack on freedom".

In what could be seen as another subtle sign of support, she and Trudeau shook hands in front of table at her Windsor Castle home, west of London, with a large bouquet of yellow and blue flowers -- the colours of Ukraine.

At a Downing Street news conference after meeting Johnson and Rutte, Trudeau said he congratulated her on becoming the first British monarch in history to reign for 70 years.

"I was able to talk a little bit about the situations we're facing and draw on her long experience for having seen much over these past decades," he told reporters.

He added: "I have the particular privilege of having known Her Majesty for about 45 years now and I can tell you that in my conversation with her this morning, she was as insightful and perspicacious as ever, very interested in what's going on."

The queen, who came to the throne in 1952, has visited Canada more than 20 times and in the 1970s met a young Trudeau when his father, Pierre, was prime minister.

Canada is one of the 14 Commonwealth countries outside the UK where she is also queen and head of state.

A lot better

Buckingham Palace announced on February 20 that the queen had tested positive for coronavirus and she was forced to cancel a series of appointments with foreign diplomats.

News that she had "mild" symptoms of Covid-19 heightened fears for her health that have lingered since she had an unscheduled overnight stay in hospital last October.

She was forced to slow down on medical advice and cancelled a number of public engagements, including hosting world leaders at the UN climate change summit last November.

Her public appearances have become rarer since, and in one recent audience she complained of mobility problems. She has been seen walking with a stick, and is visibly frailer.

But Prince Charles told members of the public on a royal visit last week that his mother, who turns 96 next month, was now feeling "a lot better".

She returned to public engagements last week, hosting a number of new foreign ambassadors by videolink, and is due at two public events next week and later this month.

Next Monday, she is scheduled to attend the Commonwealth Service at Westminster Abbey in central London and a memorial for her late husband at the same venue on March 29.

Prince Philip, her husband of 73 years, died aged 99 last April.

Public celebrations are being planned for the queen's Platinum Jubilee in early June. 

Senior royals are preparing for a series of overseas visits in the coming weeks, including Charles and his second wife Camilla, heading to Ireland.

His eldest son, second-in-line Prince William and his wife Catherine are due in the Caribbean to visit Belize, The Bahamas and Jamaica.