Veterans of last year's civil war in Libya have come to the frontline in Syria, helping to train and organise rebels, a Libyan-Irish fighter has claimed.

He told Reuters conditions in Syria are much worse than those in the battle against ousted Libyan leader Muammar Gaddafi.

Hussam Najjar, from Dublin, has a Libyan father and an Irish mother, and goes by the name of Sam.

A trained sniper, he was part of the rebel unit that stormed Col Gaddafi's compound in Tripoli a year ago, led by Mahdi al-Harati, a powerful militia chief from Libya's western mountains.

Mr Harati now leads a unit in Syria that is made up mainly of Syrians, but also includes some foreign fighters, including 20 senior members of his own Libyan rebel unit.

Mr Najjar said Mr Najjar asked him to join him from Dublin a few months ago.

The Libyans aiding the Syrian rebels include specialists in communications, logistics, humanitarian issues and heavy weapons, he added.

They operate training bases, teaching fitness and battlefield tactics.

Mr Najjar said he was surprised to find how poorly armed and disorganised the Syrian rebels were, describing Syria's Sunni Muslim majority as far more repressed and downtrodden under Mr Assad than Libyans were under Col Gaddafi.

He said: "I was shocked. There is nothing you are told that can prepare you for what you see.

"The state of the Sunni Muslims there - their state of mind, their fate - all of those things have been slowly corroded over time by the regime.

"I nearly cried for them when I saw the weapons. The guns are absolutely useless. We are being sold leftovers from the Iraqi war, leftovers from this and that.

"Luckily these are things that we can do for them: we know how to fix weapons, how to maintain them, find problems and fix them."

In the months since he arrived, the rebel arsenal had become "five times more powerful", he said.

Fighters had obtained large calibre anti-aircraft guns and sniper rifles.

Rebel efforts poorly coordinated

Disorganisation is a serious problem. Unlike the Libyan fighters, who enjoyed the protection of a NATO-imposed no-fly zone and were able to set up full-scale training camps, the rebels in Syria are never out of reach of Mr Assad's air power.

Mr Najjar said: "In Libya, with the no-fly zone, we were able to build up say 1,400 to 1,500 men in one place and have platoons and brigades. Here we have men scattered here, there and everywhere."

Although many rebel units fight under the banner of the Free Syrian Army, their commands are localised and poorly coordinated, Mr Najjar said.

"One of the biggest factors delaying the revolution is the lack of unity among the rebels," he said.

"Unfortunately, it is only when their back is up against the wall that they start to realise they should [unite]."

Syria's uprising has evolved into an all-out civil war with sectarian overtones, pitting the mainly Sunni rebels against security forces dominated by Mr Assad's minority Alawite sect, an offshoot of Shia Islam.

Mr Assad is backed by Shia-led Iran and opposed by most Arab states, which are ruled by Sunnis.

"This is not just about the fall of Assad. This is about the Sunni Muslims of Syria taking back their country and pushing out the minority that have been oppressing them for generations now," Mr Najjar said.

The presence of foreign fighters is a sensitive issue for Syria's rebels.

Mr Assad's government has taken to referring to the rebels as "Gulf-Turkish forces", accusing the Sunni-led Arab Gulf states and Turkey of arming, funding and leading them.

Mr Harati's unit is known as the Umma Brigade, referring to the global community of Muslims.

Mr Najjar said thousands more Sunni fighters from the Arab world were gathering in neighbouring countries prepared to join the cause.

Mr Harati is reluctant to enlist them because he does not want his cause tarnished by the perception that foreign Islamists are linked to al-Qaeda, Mr Najjar said, but he said that many of the foreigners were making their way to Syria on their own.