The United States is appalled by Iran’s execution of Alireza Akbari, U.S. Secretary of State Antony Blinken said, vowing that Tehran’s abuses in its crackdown of widespread demonstrations will not go unpunished.

“We were appalled by the execution of Mr. Akbari just as we’ve been appalled by everything we’ve been seeing on the streets of Iran over the last months since these protests began: mass arrests, sham trials, the executions, the use of sexual violence as a tool for protests’ suppression,” Blinken said at a news conference.

“These abuses will not go without consequence. Together with many other countries, we’ve been moving forward with a variety of unilateral actions, multilateral measures, using U.N. mechanisms, to try to hold Iran to account,” he added.

Akbari, 61, a British-Iranian national who once served as Tehran’s deputy defence minister, was handed a death sentence on charges of spying for Britain.

London has said the charges against him were politically motivated. It repeatedly called for his release. Following the execution, it imposed sanctions on Iran’s Prosecutor General

The execution drew widespread condemnation and looks set to further worsen Iran’s long-strained relations with the West, which have deteriorated since talks to revive its 2015 nuclear deal hit deadlock and after Tehran unleashed a deadly crackdown on protesters last year.

At the same news conference, British foreign minister James Cleverly said the United Kingdom would not limit itself to the response that it had already announced, although he declined to detail what more it might do.