WASHINGTON (AP) — U.S. officials say an unclassified Navy computer network was breached about two weeks ago by hackers believed to be linked to Iran.

Officials say it appears the hackers may been working as proxies for the Iranian government. Cyberattacks originating in Iran have been a persistent issue for U.S. government and businesses, particularly energy companies.

Officials would not discuss the details of the incident but said it was a low-level intrusion into the Navy Marine Corps Intranet.

Officials: Iranian Linked Hackers Breached U.S. Navy Computer Network

Hasan Rouhani, President of the Islamic Republic of Iran, addresses the 68th United Nations General Assembly at UN headquarters, Tuesday, Sept. 24, 2013. (AP Photo/Brendan McDermid, Pool)

Cybersecurity experts have said Iran has been escalating its efforts to infiltrate U.S. networks, but other intelligence officials said they have seen a fairly consistent level of activity.

The officials spoke on condition of anonymity because they were not authorized to discuss it by name.

The Wall Street Journal first reported the breach.