A string of incidents during construction of the nuclear power station has raised questions over its safety among EU countries, particularly neighbouring Lithuania.

The launch comes as Belarus strongman leader Alexander Lukashenko faces historic protests over his claim to victory in August presidential polls which Western leaders and critics say were fraudulent.

Ahead of the vote, Lukashenko had hailed the plant -- commissioned to ease the countries dependence on energy imports -- as a "breakthrough into the future".

"The turbo generator of the first reactor of the Belarusian Nuclear Power Plant was connected to the unified electricity system of the country," the Belarus energy ministry said.

The power station has proved divisive within Belarus which suffered long-lasting consequences of the Chernobyl disaster and abroad due to its location around 20 kilometres (12 miles) from the border with Lithuania.

Lithuania's Foreign Minister Linas Linkevicius criticised the launch saying it had gone ahead despite unresolved safety issues and described the energy project as "geopolitical".

The EU and the international community "simply cannot stay indifferent to such cynical ignorance," Linkevicius wrote on Twitter.

- Security threat -

Lithuanian Energy Minister Zygimantas Vaiciunas said the Russian-constructed plant constituted a "threat to our national security and our citizens".

The electricity grids of the Baltic states were historically linked to Russia and Belarus, but over the last decade new connections have opened with Sweden and Poland, allowing the Baltic energy market to open to competition.

An agreement was signed by Estonia, Latvia and Lithuania two years ago to transition their power grids to the EU by 2025.

Following the launch on Tuesday, Lithuania said it had immediately stopped electricity imports from Belarus.

Latvia said it had also blocked imports of energy generated at the plant and vowed not to purchase electricity from Russia if Moscow was unable to prove imports did not originate from the plant in Belarus.

Lithuania has offered free iodine tablets to around half a million people living close to the Belarus border to help protect them from radiation in case of an accident.

Some 130,000 people received iodine from pharmacies in the capital in recent weeks, Mindaugas Samkus, a spokesman for the Centre of Registers, a government agency, told AFP Tuesday.

Lithuania last year held four-day national emergency nuclear drills, testing sirens and screening warning messages on state-run media. The drills also involved evacuation exercises.

The Belarusian energy ministry said in August that the plant's two reactors would eventually supply one third of the country's energy requirements.

The station was constructed by the Russian state nuclear agency Rosatom, costing some $11 billion (9.3 billion euros) and largely funded by a Russian loan.

Rosatom earlier shrugged off safety concerns, saying the plant fully meets international norms and recommendations.

But over the course of construction, several reported accidents and deaths on the construction site raised safety concerns both within Belarus and abroad.

In 1986, an accident at the Chernobyl power station located on the territory of Soviet Ukraine contaminated around a quarter of Belarus's territory.

The power station's launch takes place against the backdrop of historic protests against Lukashenko, whose opponents demand that he hand over power to opposition leader Svetlana Tikhanovskaya in exile in Vilnius.