Iran has successfully test-fired an improved version of a medium-range missile, state television has said.

伊朗国家电视台报道，伊朗成功试发射一枚改进版的中程导弹。

TV pictures showed the launch of the Sajjil-2 rocket, which experts say has the range to be able to hit Israel and US bases in the Gulf¹.

Correspondents say it is not the first time this missile has been tested, but the timing² is likely to add to current tension over Iran's nuclear ambitions.

The West says Iran is trying to build nuclear weapons, a charge Iran denies.

The US said the test "undermined暗地里破坏 Iran's claims of peaceful intentions".

"Such actions will increase the seriousness and resolve决心，解决 of the international community to hold Iran accountable for负责 its continued defiance蔑视，挑战 of its international obligations on its nuclear programme," a White House spokesman said.

UK Prime Minister Gordon Brown said the missile launch could boost the likelihood可能性，可能 of further sanctions against Iran.

"This is a matter of serious concern to the international community and it does make the case for us moving further on sanctions," he said.

The French Foreign Ministry⁴ said the launch was "very worrying".

"A test of this kind can only strengthen the international community's worries at a time that Iran is also developing a nuclear programme with no identifiable civil objective in violation⁵ of five United Nations Security Council resolutions," spokesman Bernard Valero said.

In September, Iran was heavily criticised after testing its Sajjil and Shahab missiles which could travel 2,000km (1,243 miles).

Those tests came just weeks after Iran revealed the existence of a previously⁶ secret nuclear facility in the mountains near the city of Qom.

Readiness

Like the missiles tested in September, the missile launched on Wednesday uses solid fuel in its two-stage rocket.

Solid fuel rockets can be prepared for launch in less time than those using liquid propellant液体推进器 rockets.

BBC defence correspondent Nick Childs says the government's refinements⁷ to its rocket programme will increase tensions over Iran's nuclear ambitions.

The six nations negotiating with Iran on that issue want to prevent the government from enriching uranium to weapons-grade.

Iran has declared it will open 10 more nuclear sites and enrich uranium铀 to a higher degree than it has publicly announced before.

Arrest threat?

The latest test-firing comes on the same day that Iran's judiciary司法部，法官 announced it had evidence that opposition⁸ leaders had tried to foment煽动，挑起 anti-government tension on the streets following disputed elections in June.

The announcement by judiciary chief Sadeq Larijani is seen as an indication指示，象征 that opposition leaders may be about to be arrested.

Hundreds of protesters have been detained and five have been sentenced to death by courts.

Protests have continued and Iran accuses the reformists of being influenced and aided by the West.

The missile launch may be an attempt to distract attention from plans to arrest the opposition leaders, correspondents say.