Russia has accused Nato and the US of "provoking a new level of tension" after the US and Germany became the latest Ukraine allies to let the war torn country’s military use donated weapons to strike targets inside Russia.

Kremlin spokesman Dmitry Peskov said Nato countries, especially the US and several European countries, had "entered a new round of escalating tension and they are doing this deliberately", in remarks quoted by the Tass news agency.

"They are in every possible way provoking Ukraine to continue this senseless war."

However, Nato Secretary-General Jens Stoltenberg dismissed the renewed Russian threats of escalation.

“There is nothing new," he said. "This is part of President Putin's efforts to prevent NATO allies from supporting Ukraine."

Nato foreign ministers are meeting in the Czech capital on Friday to prepare for this summer’s full leaders' summit as the alliance boosts support for Ukraine.

A Berlin spokesman said Germany was convinced Ukraine had the right to defend itself from Russia, especially from cross-border attacks on its second largest city Kharkiv.

US officials said American-supplied weapons could be used to counter Russian fire near the Kharkiv region, either where Russian forces were "hitting them or preparing to hit them".

Ukraine's President Volodymyr Zelensky said the decision would help protect civilians living in villages close to the Russian border.

The chorus of allied voices giving greater leeway for Ukraine to use their weapons grew louder in recent weeks after Russia launched artillery strikes on Kharkiv from its territory, prompting appeals for help from Kyiv.

“This is a matter of upholding international law – Ukraine’s right to self-defence,” Stoltenberg said. “Russia has attacked Ukraine, (who have) the right to defend themselves. And that includes also attacking military legitimate targets inside Russia.”

“If you look at the battlefield now, Russia is launching attacks on Ukraine’s soil from Russian soil with artillery, missiles, and massing troops,” he said. “And, of course, it makes it very hard for Ukraine to defend themselves if they are not allowed to use advanced weapons to repel those attacks.”

Russia has exploited a lengthy delay in the replenishment of US military aid and Western Europe’s inadequate military production that has slowed crucial deliveries to the battlefield for Ukraine.

NATO is celebrating its 75th anniversary this year, and leaders will meet in Washington in July to reaffirm their support for the Ukrainian effort. Stoltenberg said he expects to be able to announce at the summit that at least two-thirds of members are meeting their commitment to spend 2% of their gross domestic product on defence.