A US federal judge has awarded a Washington Post journalist and his family nearly $US180 million ($265 million) in their lawsuit against Iran over his 544 days in captivity and torture while being held on internationally criticised espionage charges.

Key points: US District Judge Richard J Leon says Iran threatened to kill Rezaian

US District Judge Richard J Leon says Iran threatened to kill Rezaian Iran never responded to the lawsuit

Iran never responded to the lawsuit Martin Baron, executive editor of the Post, describes Rezaian's treatment by Iran as "horrifying"

The order in the case filed by Jason Rezaian came as Iranian officials appeared to begin restoring the internet after a week-long shutdown amid a security crackdown on protesters angered by Government-set gasoline prices sharply rising.

US District Judge Richard J Leon entered the judgment in Washington on Friday (local time) in Rezaian's case, describing how authorities in Iran denied the journalist sleep, medical care and abused him during his imprisonment.

"Iran seized Jason, threatened to kill Jason, and did so with the goal of compelling the United States to free Iranian prisoners as a condition of Jason's release," the Judge said in his ruling.

The judge later added: "Holding a man hostage and torturing him to gain leverage in negotiations with the United States is outrageous, deserving of punishment and surely in need of deterrence."

Iran never responded to the lawsuit despite it being handed over to the Government by the Swiss Embassy in Tehran, which oversees US interests in the country.

Iran's mission to the United Nations did not immediately respond to a request for comment.

Rezaian and his lawyers did not respond to a request for comment either.

'Horrifying treatment'

Martin Baron, the executive editor of the Post, said in a statement that Rezaian's treatment by Iran was "horrifying".

"We've seen our role as helping the Rezaians through their recovery," Mr Baron said.

Rezaian was tortured and threatened during his imprisonment in Iran. ( AFP: Brendan Smialowski )

"Our satisfaction comes from seeing them enjoy their freedom and a peaceful life."

Rezaian's case began with his 2014 gunpoint arrest alongside his wife Yeganeh Salehi and became a stark example of the Islamic Republic's practice of detaining those with Western ties to use in negotiations.

It is a practice recounted by human rights groups, UN investigators and the families of those detained.

Despite being an accredited journalist for the Post with permission to live and work in Iran, Rezaian was taken to Tehran's Evin prison and later convicted in a closed trial before a Revolutionary Court on still-unexplained espionage charges.

Rezaian was released in 2016 as part of a prisoner swap that culminated with the nuclear deal being sealed.

It remains unclear how and if the money will be paid.

It could come from the United States Victims of State Sponsored Terrorism Fund, which has distributed funds to those held and affected by Iran's 1979 student takeover of the US Embassy in Tehran and subsequent hostage crisis.

Rezaian named Iran's paramilitary Revolutionary Guard, this year designated as a terrorist organisation by the Trump administration, as a defendant in the case.

AP