Beirut/Jerusalem: Lebanon's Hezbollah said its fighters had fired a rocket targeting the Mossad spy agency headquarters near Tel Aviv on Wednesday, an escalation in the conflict with Israel that moved the arch-foes closer to full-fledged war.

The Israeli military said a single surface-to-surface missile was intercepted by air defence systems after it was detected crossing from Lebanon. Warning sirens sounded in Tel Aviv, Israel's economic capital.

There were no reports of damage or casualties, and the military said there was no change to civil defence instructions for central Israel.

Israeli military spokesman Nadav Shoshani said he could not confirm what Hezbollah's target was when it fired the missile from a village in Lebanon.

"The result was a heavy missile, going towards Tel Aviv, towards civilian areas in Tel Aviv. The Mossad headquarters is not in that area," he said.

Warning sirens also sounded in other areas of central Israel, including the city of Netanya. The Israeli military has been carrying out its heaviest air strikes of the conflict this week, targeting Hezbollah leaders and hitting hundreds of targets deep inside Lebanon.

Hezbollah has blamed Mossad for the recent assassination of its leaders and the blowing-up of communications devices used by its members.

Since Monday morning, the Israeli offensive has killed 569 people, including 50 children, and wounded 1,835 in Lebanon, Health Minister Firass Abiad told Al Jazeera Mubasher TV.

Half a million people are estimated to have been displaced in Lebanon, Foreign Minister Abdallah Bou Habib said. In Beirut, thousands of people who fled from southern Lebanon were sheltering in schools and other buildings.

The Iranian-backed Hezbollah has fired hundreds of missiles and rockets at Israel in recent days as the months of conflict across the border with southern Lebanon has intensified.

Also on Wednesday, the Israeli military said a drone crossing into Israeli territory from Syria was intercepted by fighter jets south of the Sea of Galilee.

The Islamic Resistance armed groups in Iraq said in a statement they had attacked a target in the occupied Golan Heights via a drone.

Shift of focus
After almost a year of war against the Palestinian militant group Hamas in the Gaza Strip on its southern border, Israel is shifting its focus to the northern frontier, where Hezbollah has been firing rockets into Israel in support of Hamas, also backed by Iran.

Israel military leaders have said they are prepared for a range of options as it battles Hezbollah, a more sophisticated, disciplined and experienced enemy than Hamas.

Israeli troops have been training for months for a possible ground operation inside Lebanon aimed at securing its northern border and enabling thousands of Israeli residents who fled for their safety to return to their communities, one of Prime Minister Benjamin Netanyahu's government's top war priorities.

Israel's close ally the United States is sticking by it despite its concerns about civilian casualties. While Arab states have condemned Israel's military campaigns, they have not taken strong steps that would force it to rein in the most powerful military in the Middle East.

On Tuesday, a strike in Beirut killed senior Hezbollah commander Ibrahim Qubaisi, who headed the group's missile and rocket force. He is one of several key figures who have been assassinated since the fighting broke out between Israel and Hezbollah nearly a year ago in parallel with the Gaza war.

'Lebanon is at the brink'
The new offensive against Hezbollah has stoked fears that conflict between Israel and Hamas in Gaza is widening and could destabilise the Middle East.

The U.N. Security Council said it would meet on Wednesday to discuss the conflict.

"Lebanon is at the brink. The people of Lebanon – the people of Israel – and the people of the world - cannot afford Lebanon to become another Gaza," UN Secretary General Antonio Guterres said.

Israel's military said its airforce conducted "extensive strikes" on Tuesday on Hezbollah targets across southern Lebanon, including weapons storage facilities and dozens of launchers that were aimed at Israeli territory.

Israeli Defence Minister Yoav Gallant said the attacks had weakened Hezbollah and would continue.

Hezbollah "has suffered a sequence of blows to its command and control, its fighters, and the means to fight. These are all severe blows," he told Israeli troops.