Image copyright AFP Image caption The prime minister says allies must come together to combat the threat posed by IS

Britain will send military trainers to Jordan to help the country's air force in the fight against so-called Islamic State, the prime minister is to say.

Theresa May will set out measures to boost cooperation between the UK and Jordan to tackle extremism on a visit to the capital Amman on Monday.

She will also discuss supporting the country with the influx of refugees fleeing the conflict in Syria.

The prime minister will be on a three-day trip to the Middle East.

Training will be carried out in Jordan and the UK to help its air force improve its capability to strike IS targets.

'Save lives'

Mrs May is also visiting Saudi Arabia during her trip where the focus will be on strengthening trade and security ties as Britain prepares to leave the EU.

She said it was "clearly in the UK's security and prosperity interests" to support Jordan and Saudi Arabia.

"To tackle the threats we face from terrorism and from geopolitical instability, we must meet them at their source," she said ahead of the visit.

Mrs May said Jordan is on the frontline of "multiple regional crises" and working with Jordan would help "keep British people safe".

"Likewise in Saudi Arabia: we must never forget that intelligence we have received in the past from that country has saved potentially hundreds of lives in the UK," she added.

'Thorny questions'

Saudia Arabia is the UK's largest trading partner in the Middle East with goods and services exports totalling £6.6bn in 2015.

Britain supports and has helped arm the Saudi-led coalition fighting rebels in neighbouring Yemen.

The government has been criticised for its involvement with Saudi Arabia due to the deaths of civilians and a continuing famine in the region.

There has been pressure from MPs from across the political parties for a rethink of British policy.

Mrs May's visit to Saudi Arabia will reopen thorny questions over support for human rights, says the BBC's deputy political editor John Pienaar.