Blasphemy is an incendiary issue in Muslim-majority Pakistan. (Representational)

US Secretary of State Mike Pompeo on Friday urged Pakistan to do more to stop the abuse of blasphemy laws after the release of Asia Bibi, who escaped a death sentence in a case that drew international scrutiny.

Releasing an annual report on international religious freedom, Pompeo estimated that more than 40 others were serving life sentences or facing execution for blasphemy in Pakistan.

"We continue to call for their release and encourage the government to appoint an envoy to address religious freedom concerns," Pompeo said.

Blasphemy is an incendiary issue in Muslim-majority Pakistan, where mere allegations of insulting Islam have sparked lynchings, although activists say many cases stem from personal disagreements.

Bibi, a Catholic, was convicted of blasphemy in 2010 and sent to death row. Despite public protests against her, Bibi was acquitted on appeal last year and in May was able to leave for Canada.

Pompeo also strongly criticized US adversaries Iran and China, pointing to Beijing's detention of some one million Muslims, mostly from the Uighur ethnic minority group, and its "intense persecution" of Tibetan Buddhists, Christians and the Falungong spiritual movement.

While President Donald Trump's administration has often hesitated to criticize ally Saudi Arabia, the report spoke of widespread abuses in the kingdom which promotes the puritanical Wahabi school of Sunni Islam.

Quoting non-governmental groups, the report said Saudi Arabia has detained more than 1,000 minority Shiites since 2011, mostly for non-violence offenses such as participating in or promoting protests on social media.

Sam Brownback, the ambassador-at-large for international religious freedom, acknowledged disappointment since the rise of Crown Prince Mohammed bin Salman.

"I think there was a lot of hope at first in the change of leadership that things would open up substantially. We need to see actions take place in a positive direction," he told reporters.

"They continue to be one of the worst actors in the world on religious persecution," Brownback said.

In April, which was after the timeframe of the 2018 report, Saudi Arabia conducted a mass execution of 37 people, most of them Shiites.

Rights groups said one of the Saudi Shiites was crucified after being beheaded, while the UN rights chief said at least three of those executed were minors when charged.