The families of two Britons and an Irishman detained in Iraq on their return home from fighting Islamic State terrorists in Syria are pleading for their release.

Jac Holmes, 23, Joe Akerman, 37, and Joshua Molloy, 24, were arrested by the Kurdistan Regional Government (KRG) after allegedly crossing into Iraq from Syria illegally.

'Their families are obviously incredibly worried,' pro-Kurdish rights campaigner, Mark Campbell, told MailOnline. 'They make a personal appeal to the KRG to release their sons.'

Arrested: The men, including Jac Holmes (pictured left) and Joe Akerman (right) had been fighting with the Kurdish People's Protection Units (YPG)

Detained: Irishman Joshua Molloy, 24, was arrested by the Kurdistan Regional Government (KRG) in Iraq. The anti-ISIS fighter is pictured carrying the flag of his enemy

The men had been fighting with the Kurdish People's Protection Units (YPG) in Syria before deciding it was time to return home to their families.

The three men travelled to a closed border crossing and waited for help from the Iraqi Peshmerga - which never arrived.

'They were waiting there for a couple of weeks and they were getting increasingly exasperated,' Mr Campbell said.

'They decided to make their way on to the Shengal area. On Wednesday they arrived - Joe sent me a message.'

But contact with the fighters was lost, and several days later Mr Akerman's mother received a phone call informing her the three men had been arrested by KRG police.

'The latest news is they are being held somewhere in Erbil,' Mr Campbell said.

Anti-ISIS fighter: Jac Holmes first travelled to Syria in January 2015, despite no previous military training

He said they do not yet know why the men have been arrested, although it has been reported that they crossed into Iraq illegally. Mr Campbell said this is something Kurdish forces do regularly.

'They have been supporting the Kurdish people against ISIS and they really just want to come home and be with their families,' he added/

Former IT worker Mr Holmes, from Dorset, first travelled to Syria in January 2015, despite no previous military training.

In an exclusive interview with MailOnline last year, he said: 'I got sick of seeing what was going on while the British government and the rest of the West did nothing and most people knew nothing of the situation in the region, so I took it upon myself to come out here and do whatever I could to assist the people in their struggle.'

Mr Molloy, a former British Army soldier, from County Laois, Ireland, travelled to the Middle East in April last year.

In custody: It is believed the three men are being held in Erbil (pictured) following their arrests last week

His father Declan Molloy told Independent.ie: 'Joshua felt very strongly about what was happening to the minority groups in the Middle East, especially the Yazidis, but the conflict had recently become a lot more complex with Turkey and Russia getting involved, and we think Joshua thought he had played his part and was coming home.'

Mr Akerman is a former British Army soldier from Halifax, West Yorkshire.

A spokesman for the British and Foreign and Commonwealth Office told MailOnline: 'We are in contact with local authorities following the arrest of British nationals in Iraq.'

The men were among the Westerners fighting against the terror group in Syria.