Under the streets of Damascus rebel units are waging a subterranean war against the Assad regime.
Two British men who fled to Syria to fight alongside rebels today admitted preparing acts of terror.
The brother of a British jihadi fighter who featured in an Isis promotional video in Syria says he was not radicalised by his local mosque.
The twin teenage girls who are thought to have travelled to Syria are "clearly posing a threat to themselves and potentially the community," police investigating their disappearance said.
Detective Chief Superintendent Tony Mole, head of the North West Counter Terrorism Unit which is leading the investigation, said: "First, I want to stress that the welfare of these two teenagers is our overarching priority."
He added: "Two 16-year-old girls left the UK on 26 June 2014 and we believe that they have since entered Syria."
At this stage he said police don't know the location of the girls, whom ITV News understands are called Salma and Zahra Halane. Officers were trying to establish who they are with.
British firms probably supplied the chemicals that have been used to make the nerve agent sarin in Syria, according to Foreign Secretary William Hague.
In a written statement to MPs he said that between 1983 and 1986 a review of the records showed a number of companies exported substances but they had legitimate uses for producing plastics and pharmaceuticals and they were not restricted under UK or international law.
He added: "From the information we hold, we judge it likely that these chemical exports by UK companies were subsequently used by Syria in their programmes to produce nerve agents, including sarin.Some of the companies involved no longer exist."
A UK chemical trader may have sourced some of the substances in question rather than producing them in the UK, he wrote.
Hague said Britain was "playing its full part" in the international effort to eliminate Syria's programme and he expected a ship carrying chemicals to be destroyed will arrive from the country next week.
Mugshots of two men from Birmingham who travelled to Syria to fight have been released after they earlier admitted preparing to carry out terrorist attacks.
Childhood friends Mohammed Nahin Ahmed and Yusuf Zubair Sarwar, both 22, spent eight months in Syria last year, before being arrested at Heathrow Airport on their return home in January.
West Midlands Police released images of the pair posing with rifles during their visit to the war-torn country.
Judge Topolski QC has said he would not pass sentence on the two men until a Court of Appeal decision about a similar case had been heard later this summer.
However, sentencing is due to open this afternoon.
The judge earlier told the court that he was willing to offer a reduction in sentence if the defendants were to plead guilty.
He described the case as a "grave one".
The families of Mohammed Nahin Ahmed and Yusuf Zubair Sarwar urged both men to return home when they realised they had gone to fight in Syria.
Sarwar's family reported him missing to police in May last year after they found a hand-written letter from him in which said he had left to join a terrorist group called Kataib al Muhajireen (KaM)- later renamed Kateeba al-Kawthar - "to do jihad".
Days earlier he had told his family he was travelling to Turkey as part of a two-week trip organised by Birmingham City University, where he was a part-time computer science student.
West Midlands Police said the men showed the mind-set to go and join the jihad in Syria, before carrying out research, buying equipment, and finally travelling a well-trod route to get inside the battle zone via Turkey.
Two men from Birmingham who have pleaded guilty to terrorism offences today spent eight months in Syria fighting against the country's regime.
Childhood friends Mohammed Nahin Ahmed and Yusuf Zubair Sarwar, both 22, from the Handsworth area of Birmingham, spent eight months in the war-torn country last year after contacting Islamic extremists from the UK.
Two young men from Birmingham who have pleaded guilty to preparing acts of terrorism while in Syria, had lied to their parents they were actually on holiday in Turkey.
Yusuf Sarwar and Nahin Ahmed, who are both 22 and from Handsworth, bought one-way tickets in May 2013 then crossed the Syrian border to train with rebel fighters.
They were arrested by officers from the West Midlands Police counter terrorism unit when they returned to Heathrow on a flight from Istanbul in January this year.
Traces of military grade explosives were found on their clothing and pictures on their camera showed them brandishing weapons.
Two men from Birmingham who travelled to Syria to join rebel fighters have admitted to preparing to carry out terrorist acts.
Nahin Ahmed and Yusuf Sarwar, both 22, have both pleaded guilty at Woolwich Crown Court.
The men were arrested when they returned to Heathrow on a flight from Istanbul in January this year.
The Conservative MP Mark Pritchard has said that new laws should be brought in requiring the families of people who travel abroad to take part in jihad to contact police.
"I think we need to look at every measure that would increase our national security", he told Good Morning Britain.
He added that it was "incumbent" on family members to report those who had gone abroad to fight in the interest of protecting their own local communities and the national interest.