The ABC has rejected Russian claims two of its journalists acted illegally after they entered the Ukraine-occupied Kursk region.

Europe correspondent Kathryn Diss and camera operator Fletcher Yeung are accused of “illegally” crossing into Russia from Ukraine on 31 August.

The pair were escorted by a Ukrainian military unit to Sudzha, a Russian town in the Kursk region, which is now occupied by Ukraine, the ABC reported.

On Friday the Russian news agency Tass reported that the Russian Federal Security Service (FSB), the successor to the Soviet KGB, had “initiated and is investigating criminal cases” against Diss and Yeung, as well as Romanian journalist Barbu Mircea, for the crime of “Illegal crossing of Russia’s State Border”.

The crime is punishable by up to five years’ imprisonment, Tass reported.

An ABC spokesperson denied any wrongdoing, claiming that the pair entered Russia legally.

“We reject Russia’s claim that the ABC’s reporters have done anything illegal,” a spokesperson said.

“They were reporting from occupied territory in a war zone and in full compliance with international law.

“Their reporting was done in the interests of keeping the public fully informed on a story of international importance.”

The journalists were being fully supported by the ABC, the spokesperson said.

Diss and Yeung’s visit was the first time the broadcaster had entered Russia since its invasion of Ukraine in 2022 and was the subject of a 4 September report showing Sudzha’s streets “littered with broken glass, twisted metal and crumbled bricks”.

“Crossing the border here doesn’t just carry the physical risk of being in a war zone; it also means that as individuals we’re unlikely to ever be able to return to Russia,” Diss and Yeung wrote in the piece.

“Moscow has issued red notices with Interpol for several other western journalists it charged with illegally crossing its border days after Ukraine’s invasion.”

The pair join journalists from Italian, German, American and Ukrainian news outlets who are the subject of ongoing investigations after making similar journeys into Kursk.

In August, the FSB began investigating Italian journalists Simone Traini and Stefania Battistini; CNN reporter Nick Paton Walsh; Nicholas Simon Connolly, a reporter for the German broadcaster Deutsche Welle; and Ukrainian correspondents Natalya Nagornaya, Olesya Borovik and Diana Butsko, Tass reported.

“In total, since 17 August 2024, criminal cases have been initiated against 12 foreign journalists for the illegal acts in question,” the FSB said.

Since 2022, Russia has banned more than 200 Australians from entering the country, denying entry “for an indefinite term” to a host of journalists and public figures “as part of the Russophobic campaign by the collective West”, authorities stated.

Among them are the ABC journalists Sarah Ferguson, Isabella Higgins, Emily Clark and Eric Campbell, who have all reported on the Ukraine war, the ABC reported.

Former prime ministers Tony Abbott and John Howard were added to the list in June.