Syria's sectarian war goes international as foreign fighters and arms pour into country

After years of Syrian insurgents and weaponry infiltrating Iraq, now the traffic goes the other way

The attack at night was sudden and fierce, mortar rounds followed by machine-gun fire. There was panic among some of the inexperienced Syrian rebel fighters. But Sadoun al-Husseini had seen it all before.

Mr Husseini got his combat experience in Iraq, fighting first against American forces and then as a member of the "Anbar Awakening", when Sunni nationalists turned their guns against foreign fighters affiliated with al-Qa'ida.

His presence inside Syria, where an overwhelmingly Sunni uprising is taking place against Bashar al-Assad's Alawite-dominated establishment, can be interpreted as an example of the country's civil war turning into an international sectarian conflict, a source of great unease in the region. Or it could be, as the 36-year-old engineer from the Iraqi city of Ramadi insisted, an expression of solidarity with oppressed brethren sharing a common heritage.

What it does illustrate is a reversal of roles between two countries. For years after the US-led invasion of Iraq, weapons and fighters slipped in across the border from Syria. Now the roles are being reversed with the flow coming the other way, although the numbers involved remain unclear.

Ayman al-Zawahiri, Osama bin Laden's successor as head of al-Qa'ida, declared this month that it was the duty of all Muslims to take part in jihad in Syria. The organisation's Iraqi arm was, according to some American officials, responsible for recent bombings in Damascus and one in Aleppo. A message on the website of al-Qa'ida in Iraq said: "A lot of people fought side-by-side with the Islamic state of Iraq and it is good news to hear about the arrival of Iraqi fighters to help their brethren in Syria."

Mr Husseini had already been into Syria through Iraq's Anbar province. He maintained that his visit to the Idlib area, a circuitous route through Turkey, was part of a humanitarian mission. He got caught up in violence, he said, when regime forces attacked a village.

Speaking to The Independent inside Syria, he said: "Our Syrian brothers are fighting their own war. I am not involved. But it is the duty of all true Muslims to help people in this struggle. We are just trying to work out what help is needed. People in Iraq and other countries are seeing the suffering that is taking place and I am working with a group that is giving support – but it is all peaceful."

Mr Husseini acknowledged some arms may be coming across the Iraqi border. "This is something I have heard," he said. "There are plenty of guns, rocket-propelled grenades, other things one can buy in Iraq. So some businessmen are maybe doing this."

He did not want to reveal details of the group he is working with for "security reasons". But he said: "We are the same family. There may be a lot of refugees coming into Iraq and we must look after them, just as the Syrians looked after us when people from Iraq had to escape there. Yes, I have heard all this talk of al-Qa'ida doing things in Syria. But that does not have the support of true Iraqis... this is propaganda, spread inside Iraq by people who want to damage solidarity with Syria."

The Shia-dominated Iraqi government has said it is taking urgent steps to stop arms going into Syria. The office of the Prime Minister, Nouri al-Maliki, said he held a meeting at the weekend "to work on closing all the gaps over the border with Syria, which terrorists and criminal gangs are using for all kinds of smuggling, including arms".

Yet the worry of sectarian strife spilling across the region continues to grow. Yesterday, in the southern Turkish city of Antakya, a demonstration took place in support of the Syrian regime by about 3,000 people, the vast majority of them Alawites, chanting: "We shall shed our blood for you, Assad."

Inside Syria, meanwhile, the official news agency, Sana, reported that gunmen killed a state prosecutor and a judge in Idlib province. They blamed "terrorists" – a catch-all phrase the regime uses to describe anyone opposed to President Assad's rule.