Image copyright AP Image caption Corruption was a "cancer at the heart of so many problems we face", David Cameron said

Commonwealth countries must lead the fight against extremism, corruption and climate change, David Cameron has said.

Speaking after he co-chaired a meeting of 10 leaders at the Commonwealth Heads of Government Meeting in Malta, the PM said agreements had been made to counter online extremist "propaganda".

Corruption was a "cancer at the heart of so many problems we face", he added.

Meanwhile, the Queen has visited the spot where George VI landed in 1943 to present the George Cross to Malta.

She also planted a sapling of Malta's national tree, next to an olive tree she planted 10 years ago during her last state visit to the country, in 2005.

London summit

Mr Cameron - who had attended a meeting with the leaders of Botswana, Canada, Australia, Ghana, New Zealand, Trinidad and Tobago, Singapore, and Malta - urged Commonwealth countries to lead the fight against corruption.

"Corruption wrecks economies, it prevents development, it corrodes our societies", Mr Cameron said.

"It can even foment terrorism as people give up hope in good and honest government."

Media playback is unsupported on your device Media caption Happy memories for the Queen in Malta

He said there was "so much more" to be done, saying the UK will host a summit in London in May to discuss proposals.

What is the point of the Commonwealth today?

The prime minister said agreements had also been made to do more to tackle extremist material online and to "share expertise and practical prevention".

He has said a Commonwealth unit to target the "scourge" of extremism will be established, pledging £5m to help fund the unit.

It comes as Mr Cameron set out what he called the "compelling case" for extending air strikes against IS from Iraq into Syria, in Parliament on Thursday.

Image copyright Reuters Image caption The Queen toured Valletta's grand harbour in a traditional Maltese fishing boat

Image copyright EPA Image caption She also watered a native Maltese tree she planted in the gardens of San Anton Palace

Speaking on climate change, Mr Cameron also announced a new package of support for developing island states, which account for nearly half the Commonwealth's membership.

"It is vital that they benefit from a global goal and that they sign up to it. Britain is helping to make that happen," he added.

The Commonwealth Heads of Government Meeting (Chogm) is held every two years, with the focus of this meeting being climate change.

Downing Street has announced the next meeting will take place in the UK, in spring 2018.

George Cross memorial

It comes as the Queen and Duke of Edinburgh, who are also in Malta, took a boat ride across Valletta Harbour to the spot where George VI landed in 1943 to present the George Cross.

Malta was awarded the George Cross for its bravery in holding out against a siege by the Axis powers during World War Two.

A plaque marking George VI's visit, which had previously been moved to a museum, has been permanently re-installed at the Customs House.

The Queen was given a tour of the harbour in Valletta in a traditional wooden fishing boat, built in 1954, called Maryanne.

While planting a gharghar tree in the grounds of San Anton Palace, in the town of Attard, she was shown the tree she had planted a decade ago.

"Ten years ago, was it? It's quite big," she told onlookers.

On Friday, while at a banquet for Commonwealth leaders, the Queen joked that the Canadian Prime Minister Justin Trudeau had "made her feel so old" after he spoke of her historic visits to Canada.

The Canadian PM spoke of his father attending an event during a royal visit, in 1982, saying the the Queen has "seen more of Canada than most Canadians".

Image copyright Getty Images Image caption The Queen, accompanied by President of Malta, Marie Louise Coleiro Preca, inspects a guard of honour