Poland's new defence minister has announced he is declassifying the country's Warsaw Pact files. Radoslaw Sikorski said the files, which had remained secret until now, will be open to historians at the state-run Institute of National Remembrance.

The institute investigates war crimes in the Communist era. The archive reveals details about the Soviet invasion of Czechoslovakia in 1968 and the imposition of martial law in Poland in 1981.