US President Donald Trump has delivered a blunt message to European Nato members that they must spend more on defence to meet the threat from terrorism.

Speaking at Nato HQ in Brussels, Mr Trump said many countries owed "massive amounts" for failing to meet the military alliance's target to spend 2% of GDP on defence.

In the wake of the "barbaric" Manchester bombing, Mr Trump said 2% was a "bare minimum" which should be increased to allow Nato to "stop terrorism in its tracks".

There were signs of apparent disgruntlement among the European leaders lined up to hear Mr Trump's speech, which followed a moment of silence in honour of the victims of the Manchester attack.

The Herald:

Photo credit: Justin Tallis/PA Wire

French President Emmanuel Macron, Luxembourg's Prime Minister Xavier Bettel and Belgian PM Charles Michel were seen to whisper among themselves as Mr Trump took countries such as theirs to task for past underspending.

Mr Trump said he had been "very, very direct" with Nato secretary general Jens Stoltenberg and other leaders in saying that members "must finally contribute their fair share and meet their financial obligations".

"Twenty-three of the 28 member nations are still not paying what they should be paying and what they are supposed to be paying for their defence," said Mr Trump.

"This is not fair to the people and taxpayers of the United States and many of these nations owe massive amounts of money from past years and not paying in those past years."

A senior UK Government source said Theresa May was "proud" that Britain was one of five Nato states - alongside the US, Poland, Greece and Estonia - to meet the 2% target, and said she had urged other members to do the same.

The Herald:

Photo credit: Justin Tallis/PA Wire

Arriving in Brussels for the Nato summit, Mrs May said the Manchester attack had shown the need for the international community "to do more in our fight against terrorism".

She said she would be telling fellow leaders they needed to "be prepared to take responsibility and that includes more investment in defence".

Mrs May took advantage of the Nato summit to raise concerns directly with Mr Trump over leaks from US authorities of information relating to the Manchester bombing, speaking to the president as they waited to pose for the "family photo" of leaders.

"The Prime Minister expressed the view that the intelligence relationship we have with the United States is hugely important and valuable but the information must be kept secure," said the Government source.

Mr Trump later said he had ordered a Department of Justice review into the "deeply troubling" leaks, which saw bomber Salman Abedi identified in the US media before British police were ready to release his name.

"These leaks have been going on for a long time and my administration will get to the bottom of this," said the president in a statement released by the White House.

"There is no relationship we cherish more than the special relationship between the United States and the United Kingdom."

Speaking to Nato leaders, Mr Trump said: "Terrorism must be stopped in its tracks or the horror we saw in Manchester and so many other places will continue forever.

"You have thousands and thousands of people pouring into our various countries and spreading throughout and in many cases we have no idea who they are.

"We must be tough. We must be strong. And we must be vigilant.

"The Nato of the future must include a great focus on terrorism and immigration, as well as on threats from Russia and on Nato's eastern and southern borders."

Mr Trump said the US had spent more on defence over the past eight years than the other 27 Nato members combined. If other states had met the 2% target in the last year alone, there would have been an additional 119 billion US dollars available for collective defence, he said.

And he told fellow leaders: "We should recognise that with these chronic underpayments and growing threats, even 2% of GDP is insufficient to close the gaps in modernising readiness and the size of forces. We have to make up for the many years lost.

"Two per cent is the bare minimum for confronting today's very real and very vicious threats.

"If Nato countries made their full and complete contributions, then Nato would be even stronger than it is today, especially from the threat of terrorism."

Following the meeting, Mrs May will fly to join other leaders from the G7 group of leading industrialised nations for their annual summit, being held in Taormina, Sicily.

However, a senior Government source said she was expected to cut short her stay in light of events in Manchester, returning to the UK on Friday evening, missing the second day on Saturday.