Russian film director Alexei German, known for his hard-hitting dramas portraying the Stalin era and WWII including "My Friend Ivan Lapshin" and "Twenty Days Without War," died on Thursday at 74, his son said.

"Today my father died without regaining consciousness... his heart simply stopped," the director's son, also a film director, Alexei German Jr wrote in a statement posted on the Moscow Echo radio station's website.

German was born in Leningrad, now Saint Petersburg, and made his films at the city's Lenfilm studio.

He completed just four films as a sole director, but his sombre, brutally honest style was hugely influential on the current generation of directors.

"He was unique. What else could I say about the artistic talent of such a man?" said fellow Saint Petersburg director Alexander Sokurov, quoted by the Interfax news agency.

German's drama about WWII partisans, "Trial on the Road" was censored by the Soviets and though made in 1971 not released until 1985 during Mikhail Gorbachev's perestroika era because of its unvarnished portrayal of the partisans and Soviet POWs.

"My father lived his life in a worthy way. He did not betray his ideals. He did not sell himself. He did not waste himself on nonsense," his son said.

At the time of his death, he was completing a film based on a science-fiction novel called "It's Hard to be a God," a project that he had begun in 1999 but struggled to finish due to financial, technical and health problems.

"I've got serious heart problems and it has become difficult to work actively. Before I always worked extra hours, doing 12-hour days, now I can't do this," German said in a 2011 interview with Saint Petersburg news website 812 Online.

His son vowed Thursday that the film based on the novel by Arkady and Boris Strugatsky would be finished in the "foreseeable future."

"The film 'It's Hard to be a God' is practically finished. All that's left is re-recording the sound. The rest is ready. My father shot this film when he was already seriously ill, sacrificing his life for it."