Fresh Russian strikes in close proximity to NATO sites have stoked fears among some European leaders that the war between Ukraine and Russia is spilling across borders.
A Russian attack on a truck near Ukraine's border with Poland was confirmed by Polish and Ukranian officials on Sunday.
The attack marks the latest strike to hit areas near NATO nations as Moscow and Kyiv intensify their long-distance strikes to try to shift momentum in the war.
A Russian drone struck near the Ukrainian-Polish border in the small town of Yahodyn, Ukraine’s Foreign Minister Andrii Sybiha said, which is only 2km from Poland.
"Russia's barbaric strikes at the Ukraine-Poland border in Yahodyn are not just a continuation of its attacks on our state borders," Mr Sybiha said on X.
Polish border guards said that the Dorohusk-Yahodyn crossing point had briefly stopped working after the attack around 800 metres from Poland, but that the crossing had since resumed operations.
Lithuania also briefly closed Vilnius airport on Sunday, local time, in response to a possible sighting of a drone, prompting NATO to summon at least one fighter jet, the National Crisis Management Centre said.
Lithuania later said the sighting turned out to be a flock of birds.
The air alert was lifted and the airport reopened within 38 minutes, after the NATO jet made a visual identification, Lithuania's National Crisis Management Centre said.
"On initial radar readings, marks left by birds and drones can be similar," it added in a statement.
Military drones straying into the airspace of Finland, Estonia, Latvia and Lithuania are stoking concerns that the war in Ukraine is spilling over into NATO's northern borders with Russia.
In a separate statement, Ukrainian Railways said that in Volyn — another region bordering Poland, — a drone attacked the locomotive of a passenger train just 2km from the Polish border.
The company said no-one was injured.
Ukraine operates several border crossings with Poland, through which a significant proportion of the military and humanitarian aid from its allies is delivered to the country.
Russia's Defence Ministry said it had targeted infrastructure facilitating military cargoes from Europe in Western Ukraine.
Ukraine is dependent on trade and arms shipments from across the Polish, Romanian and Moldovan borders.
Russia has begun targeting Ukraine's border crossings with its Western allies in recent weeks, as part of a growing campaign by both sides to erode the other's economic infrastructure more than four years into Russia's invasion.
In India, where Russian President Vladimir Putin had been attending the BRICS summit, Kremlin spokesman Dmitry Peskov said that both Indian Prime Minister Narendra Modi and Chinese President Xi Jinping had offered help brokering a peace settlement, Russian state news agency TASS reported.
Last month, at a summit in Kyrgyzstan, Mr Modi told Mr Putin that the war must end, one of several calls for peace by leaders of nations that have traditionally strong relations with Russia.
Last month, Kazakhstan's President Kassym-Jomart Tokayev publicly told Mr Putin that he should halt the conflict along the front line, which has remained largely static this year.
Russia has ruled that out, saying Ukraine should pull back to leave the industrialised eastern Donbas region in Moscow's hands, something Kyiv has said it will never do.
Both Brazil and China, themselves founding BRICS members, have called for a resumption of peace talks.
TASS cited Mr Peskov as saying that Mr Putin had informed Mr Modi of the situation "on the ground" in Ukraine, and that Russia had not ruled out resuming three-way talks between Russia, Ukraine and the United States in October.
Overnight, hostilities showed no signs of letting up.
In the Russian-held part of Ukraine's southeastern Zaporizhzhia region, the head of Russia's state nuclear energy company Rosatom accused Ukraine of striking fuel trucks close to the Zaporizhzhia nuclear power station, Europe's largest.
The Zaporizhzhia nuclear plant has been controlled by Russia since March 2022, and remains close to the front line.
A Ukrainian military spokesperson did not immediately respond to a request for comment.
In Russia itself, the mayor of the city of Nizhnekamsk, in the Volga River region of Tatarstan, said that "civilian and industrial" targets in the city had been struck by Ukrainian drones, causing at least two deaths and several more injuries.
Mayor Radmir Belyaev did not clarify which targets had been struck, but the city hosts a major oil refinery which has been attacked in the past.
Ukrainian authorities did not immediately comment on the strike on Nizhekamsk, but did say they had struck another refinery in the southern Krasnodar region.
