A Japanese journalist held hostage by Islamist militants after being captured in Syria three years ago has been released and would be brought home as soon as possible, Japan's foreign minister said on Wednesday.

Japanese diplomats in Turkey confirmed the released man was Jumpei Yasuda, a 44-year-old freelancer who was reported to have been captured by an al Qaeda affiliate after entering Syria from Turkey in 2015.

Yasuda gave thanks for his freedom in a video released by Turkish officials.

"My name is Jumpei Yasuda, Japanese journalist. I have been held in Syria for 40 months, now in Turkey. Now I'm in safe condition. Thank you very much," a bearded Yasuda said.

Prime Minister Shinzo Abe had earlier voiced relief, while still waiting for confirmation of the identity of the freed man.

Both Abe and foreign minister Taro Kono thanked Qatar and Turkey for their co-operation in freeing the man. A government spokesperson said that no ransom was paid for Yasuda's release.

"He looks to be in good health, but our staff will check his condition and transport him to Japan as soon as possible," Kono told reporters.

Yasuda's parents spoke to reporters outside their house near Tokyo.

"Above everything else, I want to see him being fine," said his father, Hideaki Yasuda.

"When he's back, I want to tell him one thing, and that'll be 'good job hanging in there'," he said.

Yasuda's mother, Sachiko Yasuda, choked back tears as she clutched a white handkerchief.

"I could do nothing but pray. So I've been praying every day," she said.

It was not the first time Yasuda had been detained in the Middle East.

He was held in Baghdad in 2004 and drew criticism at home for drawing the government into negotiations for his release.