The United States is revoking visas of Saudi officials suspected of involvement in the death of Saudi journalist Jamal Khashoggi, said U.S. Secretary of State Mike Pompeo on Tuesday.

It was the first concrete step of punishment taken by the U.S. government after the disclosure of Khashoggi's death in the Saudi consulate in Turkey's Istanbul.

"We have identified at least some of the individuals responsible, including those in the intelligence services, the Royal Court, the foreign ministry, and other Saudi ministries who we suspect to have been involved in Mr. Khashoggi's death," Pompeo said at a press briefing Tuesday afternoon at the State Department.

Pompeo added that the United States will "continue to explore additional measures to hold those responsible accountable."

The top U.S. diplomat revealed that the State Department was working with the Treasury Department to review the applicability of Global Magnitsky sanctions, a penalty punishing those responsible for severe human rights violations, on those individuals.

Meanwhile, Pompeo repeated that the United States still considers Saudi Arabia as a "strong" ally.

During the briefing, Pompeo did not reveal the exact number of officials affected. The State Department later told media that 21 Saudis are under the visa penalties.

Khashoggi, a columnist for The Washington Post, has been missing since he entered the Saudi consulate in Istanbul on Oct. 2. The Saudi authorities said last week that Khashoggi died in a "brawl" in its consulate.

After releasing the results of its initial investigations, the Saudi Public Prosecution announced that 18 people were arrested over their alleged connections with the killing.