Dozens of soldiers have reportedly been killed after two cars loaded with explosives drove into a military camp in Syria.
It is understood the attack happened in the southern town of Deraa.
In a statement, the UK-based Syrian Observatory for Human Rights said the first car had driven into the camp and exploded, followed by the second vehicle.
It is thought the detonation of the second vehicle caused the casualties.
Syrian state television reported that two car bombs had gone off at separate locations in Deraa, saying there was "news of casualties among civilians and big material damage in the two places".
It did not mention a military target and gave no further details.
Islamist militant groups have moved increasingly to the forefront in the fight to topple President Bashar al-Assad.
Al Nusra Front, an al-Qaeda-inspired group, claimed responsibility for a suicide car bombing in Hama province on Monday that the Syrian Observatory said had killed around 50 security men loyal to Mr Assad.
The Syrian government routinely blames foreign-backed Islamist militants for the 19-month-old anti-Assad revolt, in which the Observatory says about 38,000 people have been killed.
Christian elected to lead Syrian National Council
The main Syrian opposition grouping, outside Syria, has chosen a Christian former Communist as its leader.
George Sabra said his election as head of the Syrian National Council showed that the group was not sectarian.
The Council had been accused by its international allies of being ineffective in the uprising against President Assad.
Talks are expected to take place in Qatar later today with other Syrian factions with the aim of forming a new body to secure recognition as a government in waiting.
After his election, Mr Sabra immediately appealed for arms to fight Mr Assad's forces.
"We need only one thing to support our right to survive and to protect ourselves: we need weapons, we need weapons," he told reporters.
Mr Sabra beat one other candidate to succeed Abdulbaset Sieda, a Kurd resident in Sweden, who took over from the SNC's first leader Burhan Ghalioun.
Muslim Brotherhood figure Mohammed Farooq Taifoor was elected as Mr Sabra's deputy. The Brotherhood, a moderate Islamist group with affiliates around the Arab world, is seen as the dominant force within the SNC.
Mr Sabra said his election showed that there was no sectarianism in the SNC. "The people here are Muslims and they elected a Christian," he said.
Mr Sabra comes from the mixed Damascus suburb of Qatana and marched in early street demonstrations demanding Mr Assad's removal last year before fleeing the country when secret police began targeting prominent pro-democracy campaigners.
A 65-year-old geography teacher, Mr Sabra was known as a fierce critic of Mr Assad before the uprising began.
He is close to Riad al-Turk, a famed opposition figure who still operates underground in Syria.
Mr Sabra is one of the writers of the Arabic version of the popular children's TV show Sesame Street.