The chief of US Naval operations denounced North Korea on Monday for a volley of weekend missile tests, as South Korea said the launches showed the communist regime has improved its missile accuracy. "They were very unhelpful and clearly counter to the desires of the international community for a peaceful and stable region," said Adm. Gary Roughead, referring to Pyongyang's firing of seven ballistic missiles Saturday. The tests - banned under UN resolutions - were Pyongyang's biggest display of missile firepower in three years and added fuel to tensions already running high after the North's May 25 atomic test blast. The North's missiles improved in accuracy because they landed in the same area, said South Korea's Defense Ministry. Seoul's newspaper Chosun Ilbo also reported three of the seven missiles were a new type of Scud rocket that has greater range and accuracy than previous Scud series. The paper said the Scud-ER missile has a range of up to 620 miles (1,000 kilometers). The new missile represents a fresh threat to Japan. Tokyo is about 720 miles (1,160 kilometers) from the base on North Korea's east coast from where the missiles were fired. Some other parts of Japan are closer, well within the range of a Scud-ER. Experts say ballistic missiles are not generally designed for precision strikes like cruise missiles and are more aimed at causing damage in an area they fall in. "What's important is their chemical weapons," said Kim Jin-moo, an analyst at Seoul's state-run Korea Institute for Defense Analyses. "If they (Scud missies) are tipped with chemical weapons, those become a big threat." If North Korea fires Scud-B and Scud-C missiles at designated South Korean targets, they should land within 0.6 (one kilometer) and 1.2 miles (two kilometers) of the site, respectively, he said. Scuds are single stage, liquid-fueled missiles, originally developed in the former Soviet Union, and generally known for poor accuracy. Ballistic missile programs in Pakistan and Iran were built on Scud technology. North Korea has long-range missiles as well. The Taepodong-2 has a potential range of more than 4,100 miles (6,700 kilometers), putting Alaska within striking distance. It is believed to be developing a missile with an even longer range that could potentially put the US west coast and Hawaii within striking distance. The launches on July 4 - the US Independence Day holiday - also appeared to be a poke at Washington as it moves to enforce UN as well as its own sanctions against the isolated regime for its May 25 nuclear test. The North has engaged in a series of acts this year widely seen as provocative. It fired a long-range rocket it said was a satellite in early April, and in late May it carried out its second underground nuclear test following the first in late 2006. The UN Security Council punished Pyongyang with tough sanctions focused on clamping down on North Korea's alleged trading of illicit arms and weapons-related material. The US has been monitoring a North Korean freighter because of suspicions it may be carrying illegal weapons, possibly to Myanmar. The ship, however, turned around a week ago without stopping at any port and headed toward home. Won Tae-je, a Defense Ministry spokesman, said the Kang Nam 1 was expected to arrived in the North later Monday. Separately, in Kuala Lumpur, Malaysian Foreign Minister Anifah Aman pledged to work with the U.S. to block North Korea from using the Southeast Asian nation's banks for any weapons deals. The assurance came as US envoy Philip Goldberg, in charge of coordinating the implementation of sanctions against Pyongyang, met with Malaysian officials in Kuala Lumpur. South Korean media have reported that North Korea sought payment through a bank in Malaysia for a suspected shipment of weapons to Myanmar. In Seoul, the chief nuclear negotiators from South Korea and Japan discussed how to implement a UN sanctions resolution against Pyongyang and other issues, Foreign Ministry spokesman Moon Tae-young said without elaborating.