The three-dimensional TPS-117 radar, situated in the town of Audrini, 40 kilometres (25 miles) from Latvia's border with Russia, will be able to peer some 400 kilometres (250 miles) into Russian airspace.

Latvian defence officials consider it an essential part of preparations to join the NATO military alliance. But some 20,000 people last year signed a petition against the plans, citing safety fears.

Latvian President Vaira Vike-Freiberga defended the installation of the radar at the launching ceremony.

"Latvias responsibility is to take charge of its own territorial integrity and sovereignty. We fit our plans in with the NATO common security systems and we are ready to give our contribution," her press service quoted her as saying.

"In this case our contribution is this object which is due to control an air space," she said.

Latvia, a Baltic ex-Soviet republic, is one of seven ex-communist countries on course to join NATO next year.

Signs on Friday were that residents in the area still had concerns for their safety.

Tatjana Smirnova, a teacher at Audrini local school, told AFP a visit to Germany organised by the defence ministry for locals to see a similar radar installation had helped ease her own fears, but that many villagers were still uneasy.

"Now I think that the radar will not be dangerous. I have seen a similar radar in Germany and I also studied some literature about it," she told AFP.

But she said "generally the mood of locals has not been changed and many people still think that the radar will bring bad consequences."

Airis Rikveilis, a director of the defence ministry public relations department, said the total cost of the radar was eight million lats (12,429,530 euros/14,445,648 dollars).

The defence ministry says the radar can detect objects in the air, on land and water, and was selected after a joint territory survey of the Baltic states.

Its operational range is 450 kilometres in length (280 miles) and 30 kilometres (19 miles) high, and it is one of the latest radar modifications of the US company Lockheed Martin.

It is being used by armed forces in other NATO countries, including the United States, Germany, Belgium and Italy.

The defence ministry press department said the radar fully complies with all international standards on electro-magnetic radiation.

The ministry will organise and finance health monitoring of people living in the area in order to spot any changes in the environment and public health.

This is the second radar to be installed in Latvia. The 2D radar ASR-7 went into operation in the western town of Ventspils on 16 October.

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