An 'Irish jihadi' fighting with ISIS has publicly defended the execution of British aid worker David Haines.

The fanatical convert – believed to be in his early 20s – claimed Mr Haines’ former role in the RAF justified his brutal beheading.

Tributes have been paid to murdered aid worker David Haines this weekend and he has been described as a 'British hero' by David Cameron.

Defending the killing on social media, the extremist, who is fighting in Syria, wrote: “David Haines was in the RAF for 10 years, the same RAF that bombs Muslims and gets involved in wars in the Muslim lands that has no direct threat and has nothing do do with Britain.

“Have you seen the track record of USA and UK how many innocent Muslims they have imprisoned and killed?

“Not to mention the occupation and killing campaign they support in Palestine.

“I love how the amount of westerners killed can be counted on one hand but the blood of the Muslims can run like and open tap and no one cries for them."

The jihadist was writing this weekend on the social media website Ask.fm. His account has since been suspended.

Appearing on Ask.fm using the name Muthenna ibn Abu, he was asked “What did British aid worker David Haines do to your pathetic murdering army?”

He replied: “Murdering army, lol (laugh out lout). Don’t make me laugh.

“At least we give your government the choice to save your fellow countrymen, I couldn’t say the same for your ‘murdering army’.

“Your government is hypocritical and they are brainwashing your public down the same road.”

“They actually don’t care about you, the family of (James) Foley was warned that if they raised money for his realise (sic) then they could be prosecuted.

“Many hostages from other western countries was freed because their governments took the smart choice instead of being arrogant.”

Muthenna, who describes himself as “half-Irish half-Nigerian” has previously described his life under ISIS – posing with AK-47 assault rifles.

He has encouraged Muslims as young as 16 to travel to Syria and Iraq to join the fanatical group.

He has been posting messages from Syria since early July and also uses an encrypted texting service to try to persuade others to join the jihad.

Muthenna says he is a Muslim convert and has described his own parents as "kuffars" (infidels).

A video showing Mr Haines being executed was released on Saturday night.

Mr Haines, a 44-year-old father of two, was in the RAF for 12 years before becoming an aid worker, travelling to some of the world’s most dangerous areas, including Libya, Sudan and the former Yugoslavia.

He was abducted in March 2013 just three days after arriving in Syria, where he was looking for sites for possible refugee camps for a French charity, and was handed over to ISIS.

Irish Independent