JERUSALEM — Israel confirmed on Monday that the United States Department of Justice has started an investigation into the fatal shooting of Al Jazeera journalist Shireen Abu Akleh, condemning the probe as a “grave mistake” and vowing not to cooperate.

The Israeli defense minister, Benny Gantz, made the statement on Twitter, saying Israel has made it clear to the United States “that we won’t cooperate with any external investigation.”

“We will not allow interference in Israel’s internal affairs,” he added.

Palestinian officials, Abu Akleh’s family, and Al Jazeera accuse Israel of intentionally targeting and killing the 51-year-old journalist, an American citizen who was wearing a helmet and a protective vest marked with the word “press” when she was shot last May in the occupied West Bank.

Israel has acknowledged that Israeli fire probably killed Abu Akleh, but vigorously denied allegations that a soldier intentionally targeted her.

A Justice Department spokesman did not immediately respond to a request for comment about Mr. Gantz’s statement.