A high-powered group of U.S. senators is demanding that Saudi Arabia cancel the "barbaric punishment" of a blogger sentenced to 1,000 lashes for criticizing the country's clerics, saying the floggings are particularly troubling in the wake of terror attacks driven by "religious intolerance." 

Blogger Raif Badawi has been ordered to endure 20 weekly sets of 50 lashes until he is whipped 1,000 times. Saudi authorities postponed the second round, after a doctor concluded his wounds from the first 50 lashes had not yet healed. 

But rights groups, the U.S. State Department and now U.S. lawmakers have decried the punishment as inhumane. The State Department recently urged Saudi Arabia to cancel the lashings, though officials have not elaborated on what steps they may be taking to pressure Riyadh, a key U.S. ally. 

Eight U.S. senators, in a letter to Saudi King Abdullah, warned that "further violence" against Saudi citizens expressing themselves peacefully "will unfortunately be a source of continued divergence between our two countries." 

They urged the "immediate halt" to the lashings and the prisoner's "immediate release." The senators said they share the concerns of Badawi's wife that he could be "irreparably injured or killed" if the whippings continue. They also urged the release of his lawyer, a human rights activist sentenced to 15 years in prison. 

The Jan. 16 letter was signed by: Sens. Dick Durbin, D-Ill.; Patrick Leahy, D-Vt.; Jeanne Shaheen, R-N.H.; Marco Rubio, R-Fla.; Dianne Feinstein, D-Calif.; Ron Wyden, D-Ore.; Mark Kirk, R-Ill.; and Barbara Boxer, D-Calif. 

In a pointed passage, the lawmakers lamented that the Saudi judicial system was proceeding with this sentence, even as the world mourns the victims of the Paris terror attack -- many of whom worked for the French satirical publication Charlie Hebdo, which had published cartoons of the Prophet Muhammad. 

"At a time that the world is wrestling with and mourning violence committed in the name of religious intolerance, such an example of state-sanctioned violence against peaceful religious dialogue is highly troubling and helps legitimize the extremist view that violence is a justified response to the free exercise of speech and religion," they wrote. 

Badawi was sentenced in May to 10 years in prison and 1,000 lashes for criticizing Saudi Arabia's powerful clerics and ridiculing the country's morality police on a liberal blog he founded. The Jiddah Criminal Court also ordered he pay a fine of 1 million Saudi riyals, or about $266,000. 

Badawi's first public flogging took place last Friday before dozens of people in the Red Sea city of Jiddah. The father of three was taken to a public square, his feet and hands bound, and whipped 50 times on his back before being taken back to prison. 

Rights groups and activists say his case is part of a wider clampdown on dissent in the kingdom. Criticism of clerics is seen as a red line because of their influential role in supporting government policies. The clerics' ultraconservative Wahhabi interpretation of religion is effectively the law of the land. 

The 31-year-old Badawi has been held since mid-2012 and his Free Saudi Liberals website is now closed. He was originally sentenced in 2013 to seven years in prison and 600 lashes in relation to the charges, but after an appeal, the judge stiffened the punishment. Following his arrest, his wife and children left the kingdom for Canada. 

"The notion that Raif Badawi must be allowed to heal so that he can suffer this cruel punishment again and again is macabre and outrageous," said Said Boumedouha, Amnesty International's deputy director for Middle East and North Africa. 

Both the U.S. State Department and the U.N. high commissioner for human rights have called on authorities in Saudi Arabia to cancel the punishment. 

In a statement on Jan. 8, State Department spokeswoman Jen Psaki said the U.S. is "greatly concerned" by the "inhumane" punishment. 

It remains unclear how aggressively the U.S. is pressuring the Saudis, which are cooperating with the U.S. on fighting the Islamic State and other key Middle Eastern issues. 

Asked last week at a press briefing about the steps the U.S. is taking, State Department spokeswoman Marie Harf said: "I don't think we're in the business of demanding things." 

She later said the U.S. has raised the issue privately and publicly. 

The Associated Press contributed to this report.