Syria has condemned Israel after air strikes against Damascus, saying the attacks aim "to give direct military support to terrorist groups".
President Barack Obama said he does not foresee a scenario in which he would send US ground troops to Syria.
Israel claim that Syrian government forces have used a chemical weapons likely to be the nerve gas Sarin in their fight against rebels.
The Israeli military confirmed that it carried out an air strike on Gaza but gave no further details.
A Palestinian has been killed in a blast which Hamas blamed on an Israeli air strike, a Gaza hospital told Reuters.
A motorbike has been targeted in a strike by an Israeli aircraft near a Hamas training camp in Gaza, Hamas Radio reported.
Sarin is a human-made chemical warfare agent classified as a nerve agent and is the most toxic and rapidly acting of the known chemical warfare agents. It is similar to certain kinds of pesticides, called organophosphates, but is much more potent.
- Sarin originally was developed in 1938 in Germany as a pesticide.
- Sarin is a clear, colourless, and tasteless liquid that has no odour in its pure form. However, sarin can evaporate into a vapour (gas) and spread into the environment.
Symptoms appear within a few seconds after exposure to the vapour form of sarin and within a few minutes and up to 18 hours after exposure to the liquid form.
Symptoms of exposure include:
- Runny nose and watery eyes
- Small, pinpoint pupils, blurry vision and eye pain
- Drooling and excessive sweating
- Coughing, tightness in the chest and rapid breathing
- Confusion, weakness and drowsiness
- Altered heart rate or blood pressure
Sarin is the most volatile of the nerve agents, which means that it can easily and quickly evaporate from a liquid into a vapour and spread.
Yesterday US Defence Secretary Chuck Hagel, who is visiting Israel, said that US intelligence agencies were still assessing whether chemical weapons may have been used in Syria's civil war.
– Chuck Hagel, US Defence Secretary
We, the United States, along with Israel have options for all contingencies and certainly the Syrian government's use of chemical weapons would be a game changer in crossing that red line
Syrian government forces have used chemical weapons in their fight against rebels the Israeli military's top intelligence analyst has claimed.
Brigadier-General Itai Brun told a security conference photos of victims showing foam coming out of their mouths and contracted pupils were signs that nerve gas had been used.
"To the best of our understanding, there was use of lethal chemical weapons. Which chemical weapons? Probably Sarin," Brigadier-General Itai Brun said in remarks broadcast on Army Radio.
In a transcript of Brun's speech provided by the Israeli military, he said forces loyal to Syrian President Bashar al-Assad were behind the attacks on "armed (rebels) on a number of occasions in the past few months".
The Syrian government and rebels last month accused each other of launching a chemical attack near the northern city of Aleppo.
David Cameron has held talks with Benjamin Netanyahu in which he urged the Israeli Prime Minister to take action to get the Middle East peace process back on track.
The Prime Minister told Mr Netanyahu, who was in London for Baroness Thatcher's funeral, it was "essential" to improve the economic and security situation in the occupied territories.
Foreign Secretary William Hague had warned earlier this year that hopes for a two-state solution forged by Israelis and Palestinians were "slipping away".
Israeli Prime Minister Benjamin Netanyahu has paid tribute to Margaret Thatcher as a 'truly great leader' in a series of tweets:
Israeli warplanes struck targets in the Gaza Strip today in response to rocket fire towards southern Israel.
They were the first air strikes launched by Israel since an informal ceasefire ended eight days of cross-border fighting between Israel and Hamas-ruled Gaza.
An Israeli military statement said its planes targeted "two extensive terror sites" with "accurate hits".
Palestinian officials said no one was hurt in the air strikes and no damage was reported in northern Gaza.
The air raids followed the third successful rocket attack on Israel since the November ceasefire.
The military reported that Gaza militants yesterday fired at least one rocket toward southern Israel. No one was hurt and no damage was caused.
The attack was the first since rockets were fired during President Barack Obama's visit to Israel two weeks ago.
There was no immediate claim of responsibility for the rocket fire. The Israeli military says it holds Gaza's Islamic Hamas rulers responsible for any attack against the Jewish state.