The US is to impose sanctions on Ethiopian and Eritrean officials “responsible for perpetrating” a brutal war in the Tigray region, amid growing international pressure to end the conflict.

Antony Blinken, US secretary of state, in a tweet late on Sunday, said Washington had repeatedly voiced “grave concerns over continued human rights violations and abuses” in Tigray and would take steps to place visa restrictions on those responsible.

“This includes those who have conducted wrongful violence or other abuses against people in the Tigray region of Ethiopia, as well as those who have hindered access of humanitarian assistance to those in the region,” he added in a statement.

Thousands of people are believed to have been killed and hundreds of thousands are estimated to have fled their homes since civil war erupted in November when Ethiopian prime minister Abiy Ahmed, sent in troops to quell unrest in the country’s northernmost region.

Abiy, winner of the 2019 Nobel Peace Prize, said the move was in response to attacks on Ethiopian forces by troops loyal to the Tigray People’s Liberation Front (TPLF), a regional party that ruled the country for 27 years until 2018.

On Sunday, Blinken said the new action by the US was to press for a resolution to the crisis. “The time for action from the international community is now.”

Earlier this month, Josep Borrell, EU foreign policy chief, issued a statement saying military forces had blocked humanitarian access to parts of Tigray, in what he called “a grave violation of international humanitarian law”. He added, “those responsible . . . will be held to account.”

Blinken said the visa restriction policy covered “current or former Ethiopian or Eritrean government officials, members of the security forces, or other individuals,” including regional and irregular forces in the Amhara region neighbouring Tigray and members of the TPLF, who may be “responsible for, or complicit in, undermining resolution of the crisis in Tigray”.

He said: “The United States condemns in the strongest terms the killings, forced removals, systemic sexual violence, and other human rights violations and abuses.”

The secretary of state said the US had “imposed wide-ranging restrictions on economic and security assistance to Ethiopia”, a country of 114m that has been both a strategic ally to the US in the unstable Horn of Africa and a close partner of China.

Blinken did not name the officials targeted with visa restrictions, prompting J Peter Pham, a distinguished fellow at the Atlantic Council’s Africa Center in Washington, and a former diplomat with the Trump administration in the continent, to write in a tweet that it was “curious” that Blinken did not resort to a US immigration tool “which would allow him to name and shame them”.

Ethiopia on Monday criticised the US decision. A statement from the Ministry of Foreign Affairs said: “The attempt by the US administration to meddle in its internal affairs is not only inappropriate but also completely unacceptable. Ethiopia should not be told how to run and manage its internal affairs.”

The Ethiopian government has previously said it was committed to investigating human rights abuses carried out during the fighting by an assortment of national, regional and neighbouring forces.

In recent months, evidence has surfaced of involvement of troops from Eritrea, which neighbours Tigray, to help the Ethiopian government fight the battle-hardened TPLF. On Friday, for the first time, Ethiopia accused troops from Eritrea of killing civilians in a massacre in November in the Tigrayan city of Axum.

Ethiopia’s attorney-general’s office said in a statement that Eritrean soldiers had engaged in reprisal killings after pro-TPLF forces attacked them. “The investigation indicates that 110 civilians have been killed on these dates by Eritrean troops,” the statement said, referring to November 27 and November 28. Both Human Rights Watch and Amnesty International had already blamed Eritrean troops fighting in Tigray.