A North Korean ship watched closely by the UN Navy for more than a week has changed course and was heading back the way it came, US officials said as Pyongyang threatened Wednesday it would take military action if anyone attempts to search its vessels. The Kang Nam 1 - originally thought to be bound for Myanmar with suspicious cargo on board, possibly illicit weapons - turned around and headed back north on Sunday, two US officials said. The officials, speaking in Washington on Tuesday, said they do not know where the ship was heading. According to one official, it was some 250 miles south of Hong Kong on Tuesday and was heading north. The Kang Nam 1 is the first vessel monitored under UN sanctions aimed at punishing the regime for conducting an underground nuclear test in May. The new resolution seeks to clamp down on North Korea's trading of banned arms and weapons-related material by requiring UN member states to request inspections of ships suspected of carrying prohibited cargo. The communist nation has said it would consider interception of its ships a declaration of war. On Wednesday, North Korea's main Rodong Sinmun newspaper renewed the warning. "Touching our ships constitutes a grave military provocation against our country," the paper said in commentary carried by the official Korean Central News Agency. "These acts will be followed immediately by self-defensive military countermeasures." The North's warning did not specifically mention the Kang Nam 1, which the two US officials said has been moving very slowly in recent days in a possible sign it is trying to conserve fuel. The resolution prohibits UN members from providing fuel to ships suspected of carrying banned items. The officials said they did not know what the ship's turnaround means, nor what prompted it. Myanmar's authorities had informed the North Korean ambassador that the UN member nation would not allow the Kang Nam to dock if it was carrying weapons or other banned materials, a Radio Free Asia report said. A US delegation headed by envoy Philip Goldberg, meanwhile, headed Wednesday for Beijing to discuss the UN sanctions, the State Department said. Goldberg, a former ambassador, is in charge of coordinating the sanctions' implementation. China's cooperation in enforcing the sanctions against neighboring North Korea, which counts Beijing as its main ally, is seen as crucial to encouraging the North back to nuclear disarmament talks the regime abandoned in April. Pyongyang also threatened in April to launch a long-range missile. A no-sail zone remains in effect off North Korea's east coast through July 10. An announcement cited "military drills" but there were concerns the defiant nation might test-fire short- or medium-range missiles, or even a long-range missile, in further violation of Security Council resolutions. However, there was no sign of an imminent missile launch Wednesday, an official at South Korea's Joint Chief of Staff said Wednesday. He asked not to be named, citing agency policy. In Washington, the US Treasury Department imposed financial sanctions on Hong Kong Electronics, a company located in Kish Island, Iran, accused of involvement in North Korea's missile proliferation network. That means any bank accounts or other financial assets found in the U.S. belonging to the company must be frozen. Americans also are prohibited from doing business with the firm. Meanwhile, the North's regime has sought to whip up anti-American sentiment among its hunger-stricken people with a series of state-organized rallies. KCNA said Wednesday the latest anti-US demonstrations were held through Tuesday in three provinces where participants condemned the UN resolution and what the regime calls a US plot to invade the country. Such rallies have been held since June 25, the anniversary of the 1950 outbreak of the Korean War where the U.S. fought alongside South Korea against invading troops from North Korea. The war ended in 1953 in a truce, not a peace treaty, leaving the two Koreas still technically at war.