Actor and activist Michael Sheen has said the plight of Syrian child refugees is “heartbreaking” after visiting camps for those who have fled the bloody conflict.

The Frost/Nixon star has visited Jordan and the Lebanon in his role as a Unicef ambassador, seeing the conditions in which people have lived since escaping the battle-ravaged country.

Unicef UK ambassador Michael Sheen meeting children in 1st- 3rd Grade Classes at a Unicef supported- primary school in Za'atari refugee camp in JordanUnicef UK ambassador Michael Sheen meeting children at a primary school in the Za’atari refugee camp in Jordan (Jordi Matas/Unicef/PA)

Michael said: “It’s absolutely heartbreaking to think that millions of Syrian children have known nothing but war, death and destruction their entire lives.

“As a father, meeting children and families who have fled Syria and just hearing their stories was incredibly moving, so I can’t begin to imagine the impact on the children themselves.”

He told ITV’s Good Morning Britain that the conflict is “a children’s crisis now”.

Michael SheenMichael also met children at the Saadnayel informal refugee settlement, in the Beka’a Valley, Lebanon (Jordi Matas/Unicef/PA)

Michael said he had been inspired by 13-year-old Omaymah, who lives in a refugee camp in Jordan and works to warn other girls about the dangers of child marriage.

He said: “It is children like Omaymah and her friends who are Syria’s future, and we must do all we can to help them rebuild their lives.

“Ensuring all Syrian children have access to the education and protection they so rightly deserve is the first step on this journey.”

Michael SheenThe father-of-one said the trip was “heartbreaking” (Jordi Matas/Unicef/PA)

It came as Unicef released a new report claiming an estimated 3.7 million Syrian children – a third of all young Syrians – have been born since the conflict began in 2011.

It calls for £1 billion to be raised this year to provide an education for the nation’s children, estimating that 8.4 million youngsters have been affected by the conflict.

The Unicef report, No Place For Children, said there were around 1,500 “grave violations””against children in Syria in 2015, with six out of 10 being deaths and maiming from explosions. A third of these were children killed either at school or on their way to or from it.

Half of all refugees are children, Unicef says, with 306,000 born to refugee parents since 2011. More than 15,000 unaccompanied and separated children have crossed Syria’s borders.