North Korea has threatened to attack US military bases in Japan in response to the use of nuclear-armed US B-52 bombers in joint military drills with South Korea.
The threat on Thursday came a day after Pyongyang condemned the B-52 flights as an "unpardonable provocation" and threatened military action if they continue.
"The United States is advised not to forget that our precision target tools have within their range the Anderson Air Force base on Guam where the B-52 takes off, as well as the Japanese mainland where nuclear-powered submarines are deployed and the navy bases on Okinawa," the North Korean command spokesman was quoted by KCNA news agency.
The Pentagon confirmed that B-52s, taking off from Andersen Air Force base in Guam, had flown over South Korea as part of annual joint exercises that Pyongyang insist are a rehearsal for provocation.
"We cannot tolerate the US carrying out nuclear strike drills, setting us as targets, and advertising them as strong warning messages," a spokesman for the North's supreme army command said.
Al Jazeera's Harry Fawcett, reporting from Seoul, South Korea's capital, said the latest statement from Pyongyang should be seen as a "reminder rather than an immediate threat of action".
"Whats interesting is the direct reference to B52 aircraft and the nuclear-powered submarines that the US has at its disposal," he added.
"Earlier this week, the US deputy defence secretary was here in Seoul and underlined the use of B52s in combined US-South Korean military exercises going on."
"B52s are capable of carrying nuclear weapons as is the USS Cheyenne nuclear-powered submarine, which is also taking part in the exercises."
Military tensions on the Korean peninsula are at their highest level for years, with North Korea - angered by UN sanctions imposed after its nuclear test last month - threatening a second Korean War backed by nuclear weapons.
B-52s have taken part in South Korea-US joint exercises before, but the Pentagon said it had publicised their use this time to underline US commitment to defending its South Korean ally.