Ukrainian forces shelled a building housing the local administration headquarters in the center of separatist-controlled Donetsk on Tuesday with Western-supplied weapons, the TASS news agency reported, citing Russian-installed officials.

Three people were killed in a series of strikes on Donetsk, which has been under the control of Russian-backed separatists since 2014, on Tuesday, the Russian-installed mayor of Donetsk said in a post on his Telegram channel.

A separatist official said at least one of the shells used in the attack was fired from a U.S.-made HIMARS artillery system, Russian state news agencies reported.

Western officials have warned of a possible escalation in fighting in Ukraine this week, as Wednesday marks six months since Russia's invasion.