Refugees set to arrive in the UK from Syria will have been thoroughly screened to ensure they do not pose a terrorist threat, Theresa May has said.

The first charter flight bringing people fleeing the war-torn Middle East state to the UK is expected to arrive on Tuesday.

The Home Secretary said procedures were in place to check the identity of those coming and they included some of the most vulnerable people escaping the bloodshed in Syria, which has been ripped apart by civil war and the rise of Islamic State (IS).

At least one of the attackers in the Paris atrocity is believed to have entered Europe through Greece posing as a refugee from Syria.

But Mrs May said there were multiple checks in place for those set to arrive in the UK.

The first in a series of charter flights bringing Syrian refugees to the UK will arrive in Glasgow on Tuesday as part of a programme to resettle 20,000 people from camps around the war-ravaged country.

Mrs May told BBC1's Andrew Marr Show: "We have processes in place. There are two levels of screening that take place.

"First of all, we are taking people directly from the camps. We are working with UNHCR - UNHCR take biometrics, they look at documents, they interview people, they do their own process of screening against issues like war crimes and serious criminality.

"Then there is a further check that is done once people are referred to the UK. The Home Office then undertakes further checks, further biometrics are taken."

She added: "We are ensuring that we are checking people who are coming in to the UK. Of course we are taking people direct from camps and that means we are taking some of the most vulnerable people."

Mrs May also defended the authorities' ability to track UK nationals returning from Syria where they may have been radicalised.

"It is right that just over 700 have gone to Syria. Those who are returning, they are looked at on a case-by-case basis to see if action is necessary," she said.

"Of course there may be some cases where it is possible to prosecute people who are coming back from Syria."

Read about the Syrian refugees building a new life in Scotland