United States House of Representatives speaker Paul D Ryan has called for the immediate release of Anwar Ibrahim from prison.

Taking to Twitter, Ryan said he is joining in the call to press for the jailed former opposition leader’s freedom.

“He is a prisoner of conscience and should be freed,” added the Speaker.

The tweet comes amid Anwar’s judicial review of his sodomy conviction, which is being heard by the Federal Court.

Last February, the apex court upheld the Court of Appeal’s decision to convict Anwar after he was acquitted by the High Court earlier.

The Pakatan Harapan supremo, who is currently serving a five-year prison term, has claimed that the charge against him was fabricated by his political rivals.

The government has denied this.

As for Ryan, his tweet on Anwar saw an avalanche of responses from Americans, who were more concerned about the US presidential elections, with supporters of candidate Donald Trump raining criticism on him.

This is after the Republican chief told his party members in Congress that they should feel free to stop supporting Trump if they believed it would improve their own prospects on election day.

Ryan made the call after the emergence of a 2005 video which showed Trump, the Republican nominee, demeaning women in lurid terms.

An incensed Trump lambasted Ryan as being a feckless leader, and warned that Republicans who have been disloyal risked handing victory to his Democratic rival, Hillary Clinton.

Meanwhile, Human Rights Watch deputy Asia director Phil Robertson said Malaysia's reputation is on trial in the international court of opinion.

"This entire case against Anwar Ibrahim has been politically motivated from the start, and should have never been brought into a court of first instance, much less made it to the Federal Court.

"The open question being asked by the United Nations and other governments to Malaysia and the ruling Umno party is how many more times will they sacrifice respect for human rights and good governance to try and save the political career of one government leader?" he said.