US intelligence agencies believe Syria's government has likely used chemical weapons on a small scale, the White House said, but added that President Barack Obama needed "credible and corroborated" facts before acting on that assessment.
US President Barack Obama has warned President Bashar al-Assad that any use of chemical weapons in Syria's civil war would be a "game changer" but cautioned that intelligence assessments that such weapons had been deployed were still preliminary.
Syria's prime minister has survived a bomb attack on his convoy in Damascus, as rebels struck in the heart of President Bashar al-Assad's capital.
Israeli jets have devastated Syrian targets near Damascus in a heavy overnight air raid that Western and Israeli officials called a new strike on Iranian missiles bound for Lebanon's Hezbollah.
UN war crimes investigators have reached no conclusions on whether any side in the Syrian war has used chemical weapons, the inquiry commission says, playing down a suggestion from one of the team that rebel forces had done so.
Turkey accused a group with links to Syrian intelligence of carrying out car bombings that killed 46 people in a Turkish border town, and said it was time for the world to act against the government of President Bashar al-Assad.
Another ''red line'' in the sand has been declared over the on- going civil war in Syria - a two-year conflict in which the estimated number of dead has reached at least 80,000 and the number of refugees 2.5 million.
The UN General Assembly condemned Syrian President Bashar al-Assad's forces and praised the opposition, but a decline in support for the resolution suggested growing unease about extremism among Syria's fractious rebels.
US President Barack Obama has vowed to work to bring the Syrian government and rebels to the negotiating table in Geneva in coming weeks but warned that it will be hard to get the situation under control in Syria's civil war.
Britain says it is "very likely" the Syrian government has used chemical weapons, and Turkey has announced it is stepping up testing of people fleeing the Syrian civil war for traces.
Republican senators have pressed US President Barack Obama to intervene in Syria's civil war, saying America could attack Syrian air bases with missiles but should not send in ground troops.
At least 109 people have been documented as killed and up to 400 more are likely to have died in an almost week-long offensive by forces loyal to Syrian President Bashar al-Assad on a rebellious Damascus suburb, opposition activists say.
Syrian families have been burned in their homes, people bombed waiting for bread, children tortured, raped and murdered and cities reduced to rubble in Syria's two-year-old war that has sparked a humanitarian catastrophe, the United Nations says.
The Israeli military says it fired artillery into Syria after its troops were shot at on the Israeli-occupied Golan Heights, in the latest of a series of shooting incidents on the once-quiet front.
Russian Foreign Minister Sergei Lavrov says supplying the Syrian opposition with weapons is illegal under international law, a day after Britain floated the possibility it might bypass an EU arms embargo to do just that.
March was the bloodiest month yet in Syria's two-year conflict, with more than 6000 people killed, a third of them civilians, the Syrian Observatory for Human Rights says.
Britain has dramatically expanded the scale and scope of the aid it is giving the Syrian opposition and pledged to supply armoured vehicles and chemical weapons testing kits to anti-government rebels.
The United States says it will for the first time give non-lethal aid to Syrian rebels and more than double its aid to Syria's civilian opposition, disappointing opponents of President Bashar al-Assad clamouring for Western weapons.
The longer Syria's conflict goes on, the greater the risk it will breed a new generation of battle-hardened militants who will pose a threat to Britain and other countries in Europe, British Foreign Secretary William Hague says.
Russia is sending two planes to Beirut on Tuesday to evacuate more than 100 of its citizens from Syria, Russian agencies quoted the Emergencies Ministry as saying.