COPENHAGEN, Denmark — Sweden is calling on Russia to release a Ukrainian filmmaker on hunger strike, saying it's worried about his "deteriorating health condition."

Swedish Foreign Minister Margot Wallstrom wrote Thursday on Twitter that the detention of filmmaker Oleg Sentsov "violates international law and is based on a legal process that did not meet elementary standards of justice."

Sentsov has been refusing food. He is demanding that he and 64 other Ukrainians imprisoned in Russia whom he calls political prisoners be released.

His lawyer Dmitry Dinze visited him Tuesday and said Sentsov has a very low hemoglobin level, resulting in anemia and a slow heartbeat. He's serving his sentence in a prison on the Yamal Peninsula in Siberia, a region known for its harsh conditions.