Serbia’s intelligence agencies have uncovered a Russian intelligence plot involving members of the Serbian army, President Aleksandar Vučić has said, after convening a meeting of the country’s national security council.

His comments on Thursday evening came after a video was uploaded to YouTube by an anonymous user this week, showing a purported Russian spy handing over a bag of cash to another man, whose face was blurred.

Serbian officials have identified the agent as Georgy Kleban, who served as deputy military attache at Russia’s embassy in Belgrade. It is believed he left his post last year. Vučić named the Serbian man in the video only as Z.K and said he was a retired member of the Serbian military.

He said the meeting took place last December, but did not say who had made the video. The video was not made by Serbian intelligence, but the country’s security services had obtained evidence of Kleban contacting other members of the Serbian army. “There have been 10 contacts with three sources,” said Vučić.

“Our services, both civilian and military, are intensely engaged in establishing all the circumstances related to this event,” Relja Željski, the chief of Serbian intelligence’s analytical section, told state-run broadcaster RTS. “This is a very real situation and you would be amazed how often it happens on the streets of Belgrade and other cities in the world,” he said.

Kremlin spokesman Dmitry Peskov told reporters on Thursday that he was not aware of the incident in question, but said bilateral relations should not be affected. “Relations with Serbia are a partnership of a brotherly character. Nothing can influence that,” he said. Russia’s foreign ministry said the video’s release was a “provocation” aimed at disrupting a planned visit to Moscow by Vučić next month.

The video is shot from multiple angles, suggesting a well-organised surveillance operation. Rumours and speculation swirled in Belgrade about who could have been behind the sting. Serbian newspaper Politika said it had information that the video was several years old, and that the Serbian man featured was not a government employee.

Predrag Petrović, of the Belgrade Centre for Security Policy, said there were a number of possibilities for the video’s origin, including a public signal to Serbia over Russian infiltration from western intelligence agencies, or a setup by the government to distract attention from a recent scandal involving arms trafficking. “The government is trying to suppress that scandal at any price,” he said.

Petrović said the Serbian intelligence services are riven between factions in favour of closer ties with Russia and those who favour integration with Europe. “If Serbia is to join the EU in future there will have to be a purge of the intelligence services,” he said.

Vučić has attempted to keep a delicate balance in the country’s foreign policy, reiterating a desire to join the EU and Nato but also maintaining good relations with Russia. A Russian “humanitarian centre” located in the southern city of Niš has raised alarm among western diplomats, and Serbia has also signed a free-trade agreement with the Eurasian Economic Union, a Moscow-led bloc designed to rival the EU.

Vučić gave Putin a warm welcome in Belgrade earlier this year, lavishing him with praise and gifting him a puppy, but has insisted that the country’s priorities lie with Europe. “We have a good relationship with Russia and we have no problems with Russia but we are on our EU path,” Vučić told the Guardian last year.

Earlier on Thursday, Vučić summoned the Russian ambassador over the spying incident, but he said that relations with Moscow would not suffer. “We will not change our policy towards Russia, which we see as a brotherly and friendly country ... but we will strengthen our own intelligence defences,” he said.

Serbia has closer links with Russian intelligence than any other country in the region, with frequent bilateral meetings. On Thursday, the country’s interior minister Nebojša Stefanović was in Moscow and met with Nikolai Patrushev, a hawkish Putin confidant who chairs Russia’s security council. Russian agency Interfax reported the meeting, but did not say whether the pair discussed the video.

Western intelligence services believe Russian intelligence has become newly assertive in the western Balkans in recent years, particularly in Serbia and Montenegro, where elements of the establishment are sympathetic to Moscow. One informed source described approaches to potential targets in the region as “absolutely brazen”.

In 2016, Russia’s military intelligence agency, the GRU, used Serbia as a staging post for a botched coup plot in neighbouring Montenegro. Patrushev flew to Belgrade to apologise for the incident, characterising it as a rogue operation, a source told the Guardian at the time. A source in Serbia confirmed that the plot was real and was partly planned on Serbian territory.