A large explosion has rocked the Syrian capital, followed by a fire near Damascus airport, opposition activists said. Reports suggested the Israeli military had struck a Hezbollah arms depot there.

The head of the Syrian Observatory for Human Rights Rami Abdurrahman said the explosion early on Thursday has been heard across the capital, jolting residents awake.

He said the explosion is reported to have occurred near the Damascus airport road.

Israeli Intelligence Minister Israel Katz told Israeli Army Radio: "I can confirm that the incident in Syria corresponds completely with Israel's policy to act to prevent Iran's smuggling of advanced weapons via Syria to Hezbollah in Iran. Naturally, I don't want to elaborate on this.

"The prime minister has said that whenever we receive intelligence that indicated an intention to transfer advanced weapons to Hezbollah, we will act."

Activist-operated Diary of a Mortar, which reports from Damascus, said the explosion near the airport road was followed by flames rising above the area. A pro-government site Damascus Now said the explosion was near the city's Seventh Bridge, which leads to the airport road.

A regional intelligence source told Reuters that Israeli forces had struck an arms depot belonging to the Lebanese Hezbollah group.

The depot handles a significant amount of weapons that Iran, a major regional ally of Syrian President Bashar al-Assad, sends regularly by air, the source claimed.

As many as five strikes are thought to have hit the depot.

On Wednesday France's foreign minister, Jean-Marc Ayrault, said his country's intelligence service had proof a recent chemical weapons attack in Syria had been carried out by Mr Assad's government.

Additional reporting by agencies