NATO jets have been scrambled to intercept a drone that flew over Lithuania's capital Vilnius, as the country's prime minister and president were rushed to a safe house. 

The residents of the city were told to take shelter after drone activity from near Lithuania's border with Russian ally Belarus, underlining jitters on NATO's eastern flank over incursions related to Vladimir Putin's invasion of Ukraine.

An emergency announcement from the military told people in the Vilnius region to 'immediately head to a shelter or a safe place.'

The alert, which lasted for about an hour, also led to the closure of the airspace over Vilnius Airport. 

President Gitanas Nauseda and Prime Minister Inga Ruginiene were taken to shelters, and there was also an evacuation order at Lithuania's parliament. 

It was the first major alert that sent residents and political leaders in a European Union and NATO capital rushing to shelters since Russia's full-scale invasion of Ukraine in February 2022.

'Based on the parameters we saw, it's most likely either a combat drone or a drone designed to deceive systems and lure targets,' Vilmantas Vitkauskas, head of Lithuania's National Crisis Management Centre, said. 

'The electronic countermeasures here can't tell us whether an explosive device detonated or not. It's very, very difficult.'

Based on the altitude and speed, it was probably a drone, he said, 'though we can't say at this stage exactly what kind of drone it was or where it was launched from.'

Lithuania borders Russia-allied Belarus to the east and Russia's Kaliningrad exclave to the west. Wednesday's alert came after the military said it detected drone activity in Belarus, but no drones were sighted over Lithuania.

On Wednesday, NATO Secretary-General Mark Rutte commended the alliance's reaction to several drone incidents in recent days, saying that they had been met with 'a calm, decisive and proportionate response.' 

Rutte said: 'This is exactly what we planned and prepared for,' and he blamed Russia's war on Ukraine for the problem.

In recent months, Ukrainian drones aimed at Russia have crossed or come down in NATO territory on numerous occasions. Western officials have blamed what they say is likely Russian electronic jamming of the drones. 

Russia, meanwhile, has renewed threats that it would retaliate if Ukrainian drones are launched from Baltic countries or if those countries are complicit in their use against Russia.

On Tuesday evening, Lithuanian Foreign Minister Kęstutis Budrys wrote on social media that 'Russia is deliberately redirecting Ukrainian drones into Baltic airspace while waging smear campaigns' against Lithuania, Latvia and Estonia. 

'It's a transparent act of desperation - an attempt to sow chaos and distract from a simple reality: [Ukraine] is hitting Russian military machine hard.'

Budrys' comment came hours after a NATO jet shot down a Ukrainian drone over southern Estonia. Ukraine apologised for that 'unintended incident,' without specifying what had happened.

Today, Polish Prime Minister Donald Tusk said that Russia's war in Ukraine may lead to a situation in which Poland and its NATO allies have to react strongly. 

'I want to repeat, and fortunately I am not alone today, that the Ukrainian-Russian war may soon lead to a situation where we will have to react firmly,' Tusk told a news conference.

Last week, Latvia's government collapsed following an argument over the handling of multiple incidents involving stray drones suspected to be from Ukraine. 

The defence minister was forced to quit after his party withdrew its support for him, and the prime minister then resigned. The governing coalition had been under strain for months over several other issues.

In a recent escalation of aerial attacks, Russia and Ukraine have sometimes fired hundreds of drones a day at each other.

Ukraine's air force said Wednesday that it shot down 131 out of 154 drones that Russia launched overnight. The ones that got past air defences killed three civilians and wounded 18 others, including two children, officials said.

Ukraine, meanwhile, continued its aerial campaign against Russia's vital oil industry, with the General Staff reporting its drones struck a major Russian oil refinery and a pipeline pumping station overnight.

Russian media reports also indicated that a chemical plant in the southern Stavropol region was hit and caught fire, although local officials didn't confirm any direct hit.

The UK government, a strong supporter of Ukraine's war effort, has loosened strict sanctions on Russian oil refined into diesel and jet fuel in third countries as prices rise due to the Iran war.

The waiver begins Wednesday and reflects growing supply concerns over certain fuels due to the effective blockade of the key Strait of Hormuz waterway.

That step comes two days after US Treasury Secretary Scott Bessent announced that Washington was granting a 30-day extension for countries to import Russian oil that is already in tankers at sea, a move that is meant to reduce the oil supply shortages.

The announcement marked a continued policy reversal by the Trump administration, which had previously said the sanctions on Russian oil would resume. 

Originally announced in early March, the temporary waiver on the sanctions was first renewed in April.