RUSSIA and Poland's newfound solidarity was under severe strain following claims Russian soldiers stole the credit cards of one of the victims of April's plane crash that wiped out much of Poland's leadership.

Polish authorities said Russia had detained four soldiers on suspicion of looting credit cards from the body of Andrzej Przewoznik, a historian and top Polish official. Przewoznik perished with 95 other people, including Poland's president Lech Kaczynski, when their plane went down in thick fog near Smolensk airport in western Russia.

According to Warsaw, Przewoznik's card was used to withdraw money from a cashpoint within hours of the catastrophe. Further withdrawals were made from four Smolensk cash machines over the next two days. Przewoznik's widow raised the alarm when she discovered around 6,000 zloty had vanished from her dead husband's bank account.

Poland's government spokesman Pawel Gras initially blamed Russia's OMON riot police. He said the culprits had been arrested. “The three OMON officers who did this shameful deed were detained with lightning speed thanks to cooperation between the [Polish] internal security agency and Russian special services,” Gras declared.

His comments provoked an apoplectic reaction from Russia's interior ministry, which said its officers had been wrongly accused. Describing the allegation as “cynical, sacrilegious and fictive”, Nikolai Turbovets, the head of the Smolensk region's crime police, said no OMON riot police officers had been arrested. Nor had any crimes been committed at the crash scene, he insisted. Poland clarified that those arrested were soldiers rather than police.

The row threatens to undermine the genuine closeness that has blossomed between Russia and Poland in the crash's aftermath. The Kremlin gave unprecedented assistance and access to Polish investigators, while Russia's prime minister, Vladimir Putin, flew to Smolensk with his Polish counterpart, Donald Tusk.

The Polish delegation had been travelling to a memorial ceremony to mark the anniversary of the 1940 Katyn massacre, when Soviet secret police killed thousands of Polish military officers. Przewoznik was a well-known historian and head of the council responsible for maintaining Polish war memorials.

Last month Bronislaw Komorowski, the Polish acting president, asked Medvedev to increase security around the site of the plane crash after Polish reports showed victims' personal belongings unearthed there.

The crash, in which the heads of Poland's armed forces, the governor of its central bank and many other senior officials were killed, caused shock and grief in Russia as well as in Poland, and raised hopes of better relations between the two countries.

— The Guardian, London