Moscow, 23 February 2023 (dpa/MIA) - Russia will continue developing its nuclear forces, President Vladimir Putin vowed on Thursday, one day ahead of the anniversary of Russia's full-scale invasion of Ukraine.

"As before, we will pay increased attention to strengthening the nuclear triad," Putin said in a speech published by the Kremlin for Defender of the Fatherland Day, celebrated in Russia on Thursday.

Putin raised the prospect of starting to deploy the new Sarmat intercontinental ballistic missile this year, which can be armed with nuclear warheads. This had originally been planned for 2022, however.

In addition, the serial production of the Kinshal missile is to be continued and the mass delivery of ship-based Zircon hypersonic missiles is to begin, Putin said.

"A modern, capable army and navy are guarantors of a country's security and sovereignty," the 70-year-old said.

The Kremlin leader has repeatedly spoken of a threat from NATO, arguing for example that the defence alliance aims to defeat Russia as a nuclear power in the war launched by him in Ukraine.

Russia officially suspended the "New START" nuclear disarmament treaty with the United States on Wednesday, as tensions between the two countries run high over Washington's support for Ukraine.

In his state of the nation address on Tuesday, Putin had announced a modernization of the Russian army. International military analysts have pointed to massive Russian equipment problems in its war on Ukraine.

In the west of the country meanwhile, a Russian fighter plane crashed in uninhabited territory in the Belgorod region bordering Ukraine on Thursday, according to the Defence Ministry in Moscow.

The pilot was killed, the Interfax news agency reported. The fighter jet was returning from a mission.

According to initial findings, the crash had been caused by a technical issue, Moscow said.

According to Russian sources, the border area is regularly shelled by the Ukrainians.

Governor Vyacheslav Gladkov in Belgorod said after the crash that the situation was under control.

The British Ministry of Defence said Russian forces were likely planning a new offensive against the eastern Ukrainian town of Vuhledar, despite previous failed attacks.

The regional commander "is likely under intense pressure to improve results following harsh criticism from the Russian nationalist community," the ministry wrote on Twitter, while noting it was "unlikely" he had a striking force capable of a breakthrough.

In Thursday's speech, Putin thanked all those who are deployed on Russia's behalf in what he continues to call a "special military operation" in Ukraine. 

Once again, he compared today's Russian soldiers to those who fought against Nazi dictator Adolf Hitler during World War II.

"Today our soldiers are fighting heroically against the neo-Nazism that has taken root in Ukraine. They are defending our people in our historic territories, they are fighting bravely and heroically," Putin said.

Propagandists loyal to the Kremlin also repeatedly question the territorial integrity of Ukraine, which borders Russia.

Last year, Moscow annexed four territories in the east and south of Ukraine, in violation of international law. Together with the Black Sea peninsula of Crimea, which was annexed in 2014, Russia currently occupies around 18% of Ukraine's territory.