Ukraine on Monday denied Moscow’s claims that it sent "saboteurs" into Russia.
"No, Ukraine did NOT: Attack Donetsk or Luhansk; Send saboteurs or APCs (armored personnel carriers) across the border; Shell Russian territory; Shell Russian border crossing; Conduct acts of sabotage," Ukrainian Foreign Minister Dmytro Kuleba said on Twitter.
Kuleba underlined that his country also "does not plan any such actions."
"Russia, stop your fake-producing factory now," he added.
Earlier, Russian Defense Ministry alleged that two Ukrainian armored vehicles were destroyed while trying to infiltrate Russian territory.
Five "infiltrators" were killed in the clash, said a ministry statement, in an incident that could fuel the already high tensions between the two countries, as well as the West.
"Units of the Southern Military District together with a unit of border guards of the Federal Security Service of Russia prevented a violation of the state border of Russia by a sabotage and reconnaissance group from the territory of Ukraine," it said.
The ministry also claimed that the armored vehicles entered Russia "to rescue saboteurs" who had already infiltrated the country’s territory.
"Both cars were knocked out. Five soldiers of the Armed Forces of Ukraine were eliminated, there were no casualties among the Russian military," it said.
Cross-border shelling claims
Earlier on Monday, the Russian Federal Security Service (FSB) reported the destruction of a Russian border checkpoint by a projectile fired from Ukrainian territory.
On Saturday, the Russian Investigative Committee opened a criminal case after what it called the shelling of the Rostov region from Ukraine.
According to investigators, unidentified persons fired shells from multiple missile launcher systems at border areas in the Tarasovsky district.
At least two missiles hit the ground just 300 meters from the settlement of Mityakinskaya, the investigators said.
The incidents have not been independently verified by Anadolu Agency. The US has claimed Russia is trying to invent provocations – false flag operations – in order to justify a possible invasion.
Separately, pro-Russian separatists in Ukraine's Donetsk region claimed a group of saboteurs blew up a warehouse of rocket and artillery weapons and tried to reach the Russian border.
Tensions rose dramatically in eastern Ukraine last week, with reports of a growing number of cease-fire violations, multiple shelling incidents, and evacuation of civilians from the pro-Russian separatist regions of Donetsk and Luhansk.
The US administration has accused Russia of amassing nearly 150,000 troops along the Ukrainian border and claimed an attack may be imminent.
Moscow has repeatedly denied any plan to invade Ukraine and instead accused Western countries of undermining Russia’s security through NATO’s expansion toward its borders.