President Vladimir Putin's spokesman said Friday the Kremlin was doing all it could to secure the release of two men that Ukraine says are captured Russian soldiers.
"These are Russian citizens who are in captivity," Putin's spokesman Dmitry Peskov told journalists, quoted by TASS state news agency.
"Naturally in this case, the Russian side is taking all the necessary measures to liberate them from captivity. I can't say any more."
Peskov said earlier this week that "there are no Russian soldiers" in Ukraine.
Ukraine's military has shown off two wounded Russians who had been taken prisoner during a firefight in the Lugansk region and are now in a hospital in Kiev.
The men testified during a taped interrogation that they entered the war zone nearly two months ago as part of a 200-strong reconnaissance unit from the Russian army's Main Intelligence Directorate (GRU).
A Ukrainian Security Service spokesman said the suspects had been charged with involvement in "terrorist activity".
In an interview with the Novaya Gazeta opposition newspaper published Friday, both prisoners said they had not yet received a visit from Russian embassy representatives.
Russian foreign ministry official Maria Zakharova told Echo of Moscow radio station on Friday that Russian embassy officials had not been allowed to visit the men.
"Unfortunately for more than three days, we have been refused such access," Zakharova said.
In the interview with Novaya Gazeta, one of the men, Alexander Alexandrov, denied a statement by his wife on Russian state television that he had left the armed forces.
In the interview, with a Ukrainian plainclothes officer present some of the time, Alexandrov denied the claim, saying: "I took the oath."
The Russian defence ministry previously said the men were former soldiers.
Russian lawmakers in the Duma lower house of parliament on Friday said that Russia must fight for its citizens.
"We must make more harsh demands to Kiev that it return our men to the motherland and set deadlines," the first deputy head of the ruling party faction, Franz Klintsevich, was quoted as saying by TASS.
"Whoever they are, current or not current (armed forces)... Russia must not abandon its citizens," the head of the Duma's defence committee, Vladimir Komoyedov, told Interfax news agency.