A Saudi human rights activist on Monday blamed Crown Prince Mohammed bin Salman (MBS) for the killing of journalist Jamal Khashoggi.

"Mohammed bin Salman, we know, is behind all of that [Khashoggi murder]," Yahya Assiri told the 40th regular session of the U.N. Human Rights Council in Geneva.

Speaking in a panel entitled "Saudi Arabia - Time for Accountability," Assiri addressed the human rights violations in the country, highlighting that not a single decision could be taken there without prior knowledge of the crown prince.

Stressing that the perpetrators of the Khashoggi killing were still out, Assiri slammed Saudi Arabia's unwillingness to cooperate with the U.N. Special Rapporteur on Extrajudicial and Arbitrary Executions Agnes Callamard over the investigation into the murder.

"Regarding the Khashoggi case, we ask for an international and independent investigation; without it, we cannot find the truth," Assiri, who is a political refugee in the U.K., told Anadolu Agency (AA).

Without an international probe, the Saudi government "will feel free" and will continue to commit similar crimes, the rights activist added.

Assiri also thanked Turkey for its efforts to shed light on the murder, insisting that only an international probe would reveal the truth.

"We ask the Turkish government to keep pushing for an international investigation," he said.

Reminding the officials that international pressure forced Saudis to admit their involvement in the assassination after weeks of denial, Assiri said, "We need to keep the pressure until they admit that Mohammed bin Salman is behind it."

Last week, Saudi Minister of State for Foreign Affairs Adel al-Jubair refused to discuss the Khashoggi killing during his speech at the U.N. Human Rights Council.

Khashoggi was brutally murdered inside the Saudi Consulate in Istanbul on Oct. 2, 2018. Riyadh initially denied any role in the killing but has since sought to blame his death on a botched rendition operation carried out by rogue agents.

U.S. lawmakers pledge to push Trump

Meanwhile, criticism of the government's indifference toward Riyadh regarding the killing of Khashoggi continues to boil over in the U.S. Republican and Democrat senators said on Monday they were frustrated with the Trump administration's failure to provide more information about the murder and vowed to push for a stronger response.

State and Treasury Department officials briefed the Senate Foreign Relations Committee behind closed doors on Monday evening. Lawmakers said they had learned nothing new.

"It was a complete waste of time. I knew more than they did," Republican Sen. Lindsey Graham, a close ally of President Donald Trump on many issues, told reporters.

Graham said it was time for more action but did not elaborate.

Republican Sen. Mitt Romney said: "It was not very helpful. And it was frustrating for a number of us to have made so little progress."

Bob Menendez, the committee's ranking Democrat, said new sanctions should be levied, possibly via legislation he co-sponsored with Graham. "I think the Senate's going to have to act unless it is willing to accept the death of a U.S. resident journalist as an acceptable action because of a broader relationship. I don't accept that," Menendez said.

The Trump administration missed a February deadline to report to Congress on who was responsible for Khashoggi's death. In Saudi Arabia, 11 suspects have been indicted in the murder, and officials have rejected accusations that Crown Prince Mohammed bin Salman ordered the killing. The report was required after lawmakers last year triggered a provision of the 2016 Global Magnitsky human rights act requiring the Trump administration to conduct an investigation.

"The Senate needs to act. Otherwise, Global Magnitsky will have no consequence and any administration, this one or another, can just ignore it," Menendez said.

Sen. Jim Risch, the committee's Republican chairman, has not joined the criticism of the administration but has sought more information.

"This is a work in progress, and we will not let it go," Risch said in a written statement after the briefing. It said written material from the State Department was being reviewed. Last month, the Democrat-led House of Representatives approved a rare war powers resolution that would end U.S. support for the Saudi-led coalition in Yemen. The timing of a Senate vote is uncertain.