Minsk (AFP) - Belarusian President Alexander Lukashenko slammed Russia on Friday as tensions bubbled between the two close allies in a spat over border controls.

Russia's FSB security service has ordered tougher restrictions along its frontier with Belarus after Minsk last month said it was scrapping visas for short-term visits by citizens of 80 states from February 9.

There have been no border controls between Russia and Belarus since the 1990s, when the two ex-Soviet countries signed an agreement bolstering their political and economic integration.

Strongman leader Alexander Lukashenko lashed out at what he called a "political" move by Moscow to reimpose border restrictions.

"How is this a threat to Russia's national security?" Lukashenko said at a marathon press conference that dragged on over seven hours.

"We have the right to make this decision. We are a sovereign and independent state."

He also struck out at Russia over a convoluted energy dispute, saying he would take Moscow to court for allegedly cutting oil supplies to the country after Minsk hiked transit tariffs.

The Kremlin's press service quickly hit back at Lukashenko, insisting the border measure was needed to keep Russia secure and reminding Minsk that Moscow has given it more than $6 billion in loans.

"The Russian side has and continues to offer major economic, political and other support to Belarus in light of the special allied nature of our relations," the press service said.

Landlocked Belarus has remained one of Russia's closest allies since becoming independent from Moscow when the USSR collapsed and is a member of a Kremlin-lead economic union.

But despite the tight links Lukashenko -- who has ruled with an iron fist since 1994 -- is often keen to portray himself as not dependent on Moscow.

The dispute comes after Belarus -- once dubbed the last dictatorship in Europe by the US -- has seen a thaw in ties with the West.

Lifting visa requirements for visitors from across Europe and the United States for stays of up to five days was seen as a step that could help open up the tightly-controlled country.

Like Russia's other ex-Soviet neighbours, Belarus was alarmed by Moscow's intervention in Ukraine after protesters ousted a pro-Kremlin leader in 2014.