The Kremlin characterized as "dangerous" comments by British Foreign Secretary David Cameron and French President Emmanuel Macron, which signaled their countries' direct involvement in Ukraine's operations in Russian-occupied territory.
"This is a direct escalation of tensions around the Ukraine conflict, which could potentially pose a danger to European security, to the entire European security architecture," Kremlin spokesman Dmitry Peskov said at a press conference on Friday.
"Here we see such a dangerous trend of escalating tensions in official statements. This is a reason for our concern," he said.
Even Russian Foreign Ministry spokeswoman Maria Zakharova said: "This is the first time that a Western politician has so frankly admitted what has long been a well-known secret to most countries of the world: that the West is waging a war of secretly against Russia by the hands of Ukrainians".
Russia, she added, would respond if Ukraine carried out attacks against Russian territory with British weapons.
During a visit to Kiev, David Cameron told the Reuters news agency that Ukraine has the right to attack in self-defense. "As Russia is striking inside Ukraine, you can fully understand why Ukraine has been forced to take all measures to defend itself," he said.
David Cameron pledged $3.7 billion in annual military aid to Ukraine "for as long as it takes", adding on Thursday that London had no objection to using its weapons for attacks inside Russia.
In a separate interview on Thursday, French President Macron reiterated his view that he does not rule out sending troops to Ukraine, a move Russia said would lead to a direct and dangerous escalation of tensions over the conflict in Ukraine.
Spokeswoman Zakharova said Russia was ready to consider "serious" peace proposals from Ukraine, based on what she called Moscow's existing "realities" and security concerns, including a pledge that Ukraine remain militarily neutral in the future. .
Moscow's conditions are identical to those that Ukraine has already rejected several times.
Russia also warned on Friday that it would respond with "devastating retaliatory strikes" if Ukraine strikes Crimea or the Crimean Bridge, which connects southern Russia to the Black Sea peninsula.
"The Crimean bridge is again in question," Zakharova said at the conference. "Preparations for an attack on it, which is hard to believe, are now being made openly, boldly and with the absolute direct and unabashed support of the West."
Moscow said it believed Ukraine, which was recently supplied with the MGM-140 long-range missile system by the United States, was planning to attack the bridge before or on May 9, which coincides with the anniversary of the defeat of Nazi Germany from Russia in World War II.
The Russian Black Sea Fleet, which has been repeatedly attacked by Ukraine, is stationed in Crimea.
Kiev has said it considers the construction of the road and rail bridge, which has been used in the past to move Russian troops and weaponry used against Ukraine, illegal. Kiev demands the return of Crimea under the authority of Ukraine. Russia annexed Crimea in 2014.
A Russian missile hit the central Ukrainian region of Kirovohrad on Friday, injuring a civilian and damaging homes and civilian infrastructure, a local official said on the Telegram social network.
Ukraine's energy infrastructure has been the target of intensified Russian attacks in recent months. The Russian military has hit Ukraine's energy grid with missiles and drones, while Kiev faces a serious shortage of air defense weapons.
Two people were killed Friday in a Russian attack on the town of Kurakhova, located in the eastern Donetsk region, where fierce fighting is taking place between Ukrainian and Russian forces.