Damascus military facilities 'hit by Israel rockets'
Syria has accused Israel of launching rocket attacks on Damascus, after a night of huge explosions near the city.
Syrian state media said the rockets hit the Jamraya research centre, which Western officials have suggested is involved in chemical weapons research.
Israeli radio quoted a senior security official confirming an attack, and sources said it targeted weapons bound for Hezbollah militants in Lebanon.
It is the second suspected Israeli strike in Syria in two days.
On Friday Israeli aircraft hit a shipment of missiles near the Lebanon border, according to unnamed US and Israeli officials.
The BBC's Yolande Knell in Jerusalem says the latest developments are a significant escalation in Israel's involvement in the conflict.
Two air strikes in 48 hours does indeed start to look perilously like the involvement in Syria's internal crisis the Israelis have always said they want to avoid, especially when they are visibly taking out military targets on the very edge of Damascus.
Politically such attacks strengthen the Syrian regime in regional and domestic terms, and embarrass the rebels, who are cast as actors in a Western-directed plot to undermine resistance to Israel.
Israel has said that its only concern is to prevent advanced weapons being handed over to Hezbollah. Objectively it would be hard to see Israel's interest in helping trigger an uncontrolled collapse of the regime, leaving the field open to rebel groups among which Islamist radicals currently make the running.
But if the Friday and Sunday attacks herald a pattern of mounting Israeli involvement, it may be increasingly hard to keep the two strands separate.
She says Israel has already responded to fears of retaliation by locating two batteries of its Iron Dome missile defence system near Haifa, close to the Lebanese border.'Mild earthquake'
Damascus was shaken by repeated explosions coming from the north-western suburbs.
Amateur video footage and eye witness testimony suggested rocket attacks had hit weapons dumps, triggering dramatic orange-flamed blasts.
The area houses numerous military facilities, including the Jamraya research centre, designated by Syria as a scientific research centre "in charge of raising our level of resistance and self-defence".
A state TV bulletin said: "The new Israeli attack is an attempt to raise the morale of the terrorist groups, which have been reeling from strikes by our noble army."
Damascus-based journalist Alaa Ebrahim told the BBC it was "the biggest explosion" the city had seen since the conflict began two years ago.
He said residents living near Jamraya reported feeling a "mild earthquake" just before the blast, indicating that the rockets may have hit an underground facility.
- According to Syria's Sana state news agency: "The new Israeli aggression shows the direct involvement of the Zionist entity in the conspiracy against Syria and the relationship that links the armed terrorist groups with the Israeli hostile schemes backed by the Western, regional and some Gulf states."
- Iran's Defence Minister Ahmad Vahidi is quoted by Fars news agency reacting to Friday's attack: "The inhuman acts and adventurism of the Zionist regime will strengthen the waves of anti-Zionism in the region and will shorten the life of this fake regime."
- A writer with Israel's Walla website notes that "common sense would seem to mandate" the attack on Syrian targets. However, he notes that admission of the attack from Syrian state media and the Lebanese militant group must raise fear about retaliation.
He added that the Syrian army was likely to have suffered major casualties in the attack.
The UK-based Syrian Observatory for Human Rights quoted eyewitnesses in the area as saying they saw jets in the sky at the time of the explosions.
The Jamraya facility was also apparently hit in an Israeli air strike in January.
Israeli officials confirmed the January strike, but insisted it had targeted trucks carrying missiles to Hezbollah.
After the latest attack, unnamed Western intelligence sources have again said the target was a weapons cache heading for Lebanon.
Israel has repeatedly said it would act if it felt advanced weapons were being transferred to militant groups in the region, especially Hezbollah.
Israeli military analysts are already warning of the danger of war, as what promises to be a long hot summer fast approaches”
Analysts say the air strikes are unlikely to have a major effect on the civil war in Syria.
The latest reports from coastal regions around the town of Baniyas suggest dozens of Sunnis have been massacred in a campaign of sectarian cleansing.
The government said it had pushed back "terrorist groups" and restored security to the area.
The US said it was "appalled by the horrific reports" but that it did not foresee sending US troops to Syria.
However, the US is no longer ruling out supplying weapons to the rebels.
More than 70,000 people are estimated to have been killed since the conflict erupted in March 2011.