This is the extraordinary moment a Ukrainian secret services officer infiltrated a university recruitment drive by the Russian army and warned students they face certain death if they go to war.

The masked intelligence agent posed as one of Vladimir Putin's fighters and was allowed virtually into a meeting of hundreds of would-be recruits.

Such sessions, designed to encourage students to sign army contracts, are held at universities all over Russia to boost numbers at the front, where Putin's forces are losing at least thousands of men each month, according to Ukrainian authorities. 

Footage shows the man speaking on a live link, as he tells students in a lecture hall at Kuban State Agrarian University in Krasnodar: 'I am in fact a soldier, just not Russian, but Ukrainian.

'And I want to tell you, God forbid you go there.

'I will have to kill you, every one of you who signs this contract.'

University chiefs scrambled to cut the link, but only did so after the Ukrainian officer had warned the students: 'Your faces are all [recorded], just like the rector's.'

He went on to tell the group how Russian commanders extort money from their soldiers.

'The frontline hasn't moved for four years, and it's standing still,' he made clear, referring to the Russian failure in the war.

Putin's invasion has led to 'a cemetery the size of two countries', he said.

'And, honestly, everyone who comes onto Ukrainian soil, we will kill them all.'

Embarrassed university chiefs finally cut the link, and the screens in the lecture hall went blank.

It has been four years since Russia launched its large-scale invasion of Ukraine, attacking the country from multiple directions.

The cost of the war has been high on both sides, and as Europe's biggest conflict enters its fifth year, there is no sign of any peace deal despite US diplomatic efforts over the past year. 

Russian strikes killed at least two people in Ukraine, officials said Sunday, as the Ukrainian military struck a drone factory in southwestern Russia.

A 'massive' nighttime drone strike on Chernihiv in northern Ukraine killed a 16-year-old boy and wounded four others, according to the head of the city's military administration.

Rescuers found the teenager's body as they cleared away rubble, Dmytro Bryzhynskyi reported on Telegram on Sunday morning. 

He said the drone strike also wounded three women and one man. Several houses were set on fire, he added.

Russian drones also attacked the southern city of Kherson on Sunday, local officials reported.

A man died of his wounds after a drone hit a van driving through the city centre, according to Oleksandr Prokudin, the head of the regional administration. 

A second man was hospitalised with blast injuries, regional authorities said.

Russia launched 236 drones into Ukrainian territory overnight into Sunday, Ukraine's air force reported. Of those, 203 drones were shot down while 32 hit targets in 18 separate locations, it said.

Meanwhile, Ukraine hit a drone factory in the city of Taganrog, Ukraine's General Staff reported. 

The site lies some 35 miles east of Russian-occupied eastern Ukraine in southwestern Russia.

According to the military, Ukrainian drones sparked a fire at the Atlant Aero factory, which designs and produces strike and reconnaissance drones, as well as components for more powerful UAVs that can carry guided bombs weighing up to 250 kilograms. 

Ukraine's navy said it attacked the drone factory in southern Russia, using domestically manufactured Neptune cruise missiles.

'This defence enterprise is an important part of the Russian military-industrial complex, where drones were developed and manufactured,' the navy said in an online post.

It also posted images showing a huge cloud of smoke over the city, which it said was the impact of the strikes.