Vladimir Putin has once again threatened the use of nuclear weapons after accusing Ukraine of attacking a power plant in the Kursk region.

Russia's President accused Ukrainian forces of trying to hit Kursk Nuclear Power Plant after invading the region last month.

Speaking at the Eastern Economic Forum in Vladivostok on Thursday, Putin said: "One can only imagine what will happen if we strike back; what will happen in Europe."

The BBC reported last month that Russian forces are bolstering defences around Kursk's power plant.

Russian military bloggers, including war correspondent Alexander Sladkov, allege that Ukraine has been trying to seize control of the plant.

The United Nations' nuclear watchdog chief, Rafael Grossi, warned last month that there is "the danger or the possibility of a nuclear accident has emerged near here."

"I was informed about the impact of the drones. I was shown some of the remnants of them and signs of the impact they had,” Grossi said, without saying who was responsible.

"The core of the reactor containing nuclear material is protected just by a normal roof", he said during his visit. "This makes it extremely exposed and fragile, for example, to an artillery impact or a drone or a missile.

"A nuclear power plant of this type, so close to a point of contact or a military front, is an extremely serious fact that we take very seriously."

Russian Foreign Minister Sergey Lavrov has also sent a warning to the US over reports that Washington could supply long-range weapons to Ukraine to enable them to strike territory deep within Russia.

He said: "Americans already stepped over the line that they set up. They're joking about our red lines. Don't joke about our red lines. They perfectly know where they are."

"The obsession in the fight for power for Democrats to appear cooler than Republicans or vice versa, at least now—it's leading to more and more escalation.

"I'm confident there are sensible people there who have an influence, and I hope the interests of the USA will be considered."