At 10am on Tuesday sirens wailed throughout Israel.

Israelis had been given ample warning: "Don't panic, routine drill only."

Everyone was urged to take part and to run as fast as possible to their nearest bomb shelter.

I was walking along a busy Jerusalem street when the sirens sounded.

But the general reaction was muted at best. I didn't see anyone running anywhere.

This five-day long civil defence drill has been billed by Israeli officials as the biggest in the country's history.

It is designed to simulate responses to war and other emergency situations, such as a large-scale terror attack.

Mass evacuation

But Israelis have been here before. Last year's drill was also described by their media as the biggest, most comprehensive ever.

Seen in its entirety it can be an impressive spectacle.

Dubbed "Turning Point 2", this year's exercise includes simulated missile attacks - chemical and biological - on towns.

Rescue services are to simulate mass evacuation from populated areas. Hospitals will practise treating thousands of casualties.

During the drill, Israel's security cabinet plans to convene meetings aimed at examining the effectiveness of the decision-making process during the attacks.

The Israeli cabinet was severely criticised for its performance during the July-August 2006 war with the Lebanese Islamist Hezbollah movement.

Alert raised

In addition to the decision-making process during the conflict, Israel's government and its military also came under fire for their general lack of readiness and for the resulting suffering of Israelis living in the north of country, where thousands of Hezbollah rockets landed.

In recent weeks there has been much discussion on Israeli TV and radio about newly-heightened tensions on the northern border - this time with Syria.

Israel and Syria are technically at war, though the boundary line between the two countries is usually a cold front.

Still, the potential for attack is always felt by Israel from its northern neighbours, in fact from virtually all of its Arab neighbours.

Israel only has a peace deal with Egypt and Jordan.

(Other Arab nations have offered to normalise ties if Israel pulls back to its 1967 borders and enables the founding of an independent Palestinian state.)

Israel has also recently raised its alert level in airports and embassies throughout the world in preparation for a possible attack by Hezbollah.

A ruse?

The movement has pledged "open war" with Israel, blaming it for the killing of its military commander, Imad Mughniyeh, in February.

Israel has not claimed or definitively denied responsibility.

But Israel sees its biggest existential threat as coming from Iran.

Israelis are haunted by Tehran's presumed nuclear ambitions and President Mahmoud Ahmadinejad's remarks calling for an end to the Israeli state.

This week, Israel's Minister of National Infrastructure, Benjamin Ben-Eliezer, said: "The civil defence drill does not simulate a fictitious situation.

"I think the future will be much harder than the reality we are familiar with."

Syrian and Lebanese officials have said they hope the military exercise is not an Israeli ruse to begin a new war in Lebanon.

http://news.bbc.co.uk/2/hi/middle_east/7336998.stm