FILE PHOTO - Sen. Joe Manchin, (D-WV) heads to the Senate Security Office to peruse the FBI report on sexual assault in connection with U.S. Supreme Court nominee judge Brett Kavanaugh in Washington, U.S., October 5, 2018. REUTERS/Mary F. Calvert

WASHINGTON (Reuters) - U.S. Senator Joe Manchin was notified his social media accounts had been hacked, his office said on Thursday, amid U.S. government warnings of attempts to interfere in next week’s congressional elections.

The announcement comes less than a week before elections that will determine whether Republicans will maintain control of the House of Representatives and the Senate.

Manchin, a Democrat, is fighting to hold onto his seat in West Virginia, a state in which two-thirds of voters supported Republican U.S. President Donald Trump in the presidential election two years ago.

The elections will serve as a test of polling security in the United States after intelligence agencies concluded that Russians meddled in the 2016 elections. Moscow has denied interfering in the U.S. elections.

U.S. law enforcement and intelligence agencies have warned that Russia, China, Iran and other foreign entities are also trying to interfere in the upcoming vote. Separately, the U.S. government indicted a Russian woman for conspiring to interfere with the Nov. 6 elections.

It was not immediately clear when Manchin’s accounts were hacked or by whom. It was also unclear what, if anything, had been done with the accounts when they were hacked.

Manchin’s office said in a statement that the senator and his staff were working with law enforcement officials to prevent further hacking and to secure accounts.