(The Hill) – Secretary of State Antony Blinken on Thursday confirmed that a U.S. citizen was killed in Ukraine.

Blinken said during a briefing that he had no further details about the incident yet.

Police in the Ukrainian region of Chernihiv said in a Facebook post that an American was among the people killed by a heavy artillery attack but did not detail where in the city the attack occurred.

Chernihiv is located in the northeast of Kyiv. The head of the region said the city is “suffering great losses,” according to CNN.

The Pentagon would not confirm the death.

Developing story; Laura Kelly and Ellen Mitchell contributed.