TEL AVIV (Reuters) - Israel rushed a fifth Iron Dome air defence battery into service in the Tel Aviv area on Saturday, using it within hours to shoot down a rocket fired at the coastal metropolis from the Gaza Strip.
But the successful interception, witnessed by a Reuters correspondent, appeared to stretch the capabilities of the unit meant to provide coverage for Israel's biggest conurbation, which includes its main international airport, 15 km (6 miles) inland.
Iron Dome's radars, linked with other Israeli surveillance systems, spot rocket launches from Gaza, hundreds of which have happened during cross-border fighting that erupted on Wednesday.
The detection sets off sirens in the town targeted so people can shelter while Iron Dome fires a guided interceptor missile. In the case of Tel Aviv, the military says, this alert should provide 90 seconds before the rocket closes in for impact.
But on Saturday it took less than that between the wail of the siren and the explosive collision of metal on metal over a Tel Aviv beach.
The distinctive smoke-cloud left behind, like an inverted tear-drop, was just a few hundred yards above ground - suggesting the rocket was on its final descent when it was knocked out of the sky by one of two interceptors shot at it.
Few of the hundreds of people who had ducked-and-covered on the boardwalk looked upset about what might have been a close call. It was the third rocket launch against Tel Aviv in 48 hours, without damage or casualties being caused.
"Well that wasn't such a big deal," said a woman who had watched the interception while clinging for protection to the trunk of a baby palm tree on a traffic island.
But there was no nonchalance in the faces of police specialists who streamed to the scene in search of debris that might help them determine the design of the weapon used.
Hamas, the Islamist group governing Gaza, claimed the attack and said the rocket was an Iranian-made Fajr-5, which has a 75 km (46 mile) range and a 175 kg (385 pound) warhead -- powerful enough to shear through a concrete apartment block.
Israel has been trying to bomb these on the ground, and each one that survives to be launched across the border means a boost in prestige for the outgunned Palestinian guerrillas.
The fifth Iron Dome had not been not scheduled to come into service until early 2013. The four other batteries are all deployed much further to the south, protecting towns close to the Gaza border.
A military spokeswoman said Iron Dome has shot down at least 222 incoming rockets since Wednesday -- a 90 percent success rate. Interceptor missiles are fired only when the system calculates the rocket being tracked might hit a built-up area.
Iron Dome was first deployed in April 2011, outside the southern city of Beersheba, going into action immediately in another flare-up of clashes with nearby Gaza.
At the time, defence officials said the system provided protection against rockets with ranges of between 5 km (3 miles) and 70 km (42 miles), as well as mortar bombs.
They have since acknowledged that Iron Dome had proven unreliable for missiles with ranges under 7 km (4 miles).
Made by state-owned Rafael Advanced Defence Systems Ltd, the system is truck-towed for easy transport, and Israel says it needs 13 of them for satisfactory nationwide defence.
Iron Dome, along with Israeli ballistic missile shield Arrow, has received extensive support from Washington, which seeks both to reassure and restrain the Jewish state in the face of the nuclear advances of its arch-enemy Iran.
Writing by Dan Williams and Ori Lewis; editing by Douglas Hamilton