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UNITED NATIONS — In its latest effort to bring a seemingly unyielding North Korea to heel over its nuclear weapons and ballistic missile programs, the United Nations Security Council imposed sanctions on five trading companies and five individuals on Thursday, in addition to banning the trade of two goods linked to building ballistic missiles.

The North Korean men and companies that were cited, including Hong Kong Electronics, a trading company based in the Iranian free-trade zone of Kish Island in the Persian Gulf, are the core elements of North Korea’s attempts to build nuclear weapons, diplomats said.

The sanctions include a travel ban and an asset freeze on the five individuals, although it is unclear how often they travel internationally or whether they hold any foreign bank accounts.

“The individuals are closely involved and responsible for these programs; they are very senior,” Yukio Takasu, the Japanese ambassador to the United Nations, said. “We have full confidence this will have a major impact.”

The call for new sanctions was included in a Security Council resolution that was passed in June after North Korea conducted its most recent nuclear test on May 25. The North has adopted a bellicose stance toward all United Nations actions, firing off batches of missilesto thumb its nose at the threat of additional penalties.

“This is probably not enough for a major North Korea response,” David C. Kang, a professor of international relations at the University of Southern California, said by telephone from Seoul. “It will hurt them in any attempt to sell weapons, so as a restraint it might be good. But in terms of getting them to change their behavior, I don’t believe that is going to happen.”

The country’s belligerent attitude has been linked to the question of who will succeed Kim Jong-il, the leader who is visibly ailing. South Koreans are debating whether a transition to one of Mr. Kim’s sons would bring new calm or renewed challenges to the outside world, Professor Kang said.

Western diplomats said the new sanctions were determined by consensus among the Council’s 15 members, with some horse-trading, particularly with China, North Korea’s most important trading partner and ally. The Council will investigate other companies and individuals.

The sanctioned companies are the Namchongang Trading Corporation, linked to purchases of pumps, aluminum tubes and other materials used in uranium enrichment; Hong Kong Electronics, which has transferred millions of dollars for Tanchon Commercial Bank; the Korea Hyoksin Trading Corporation, involved in the development of nuclear and other weapons; the General Bureau of Atomic Energy, which runs the nuclear program; and the Korean Tangun Trading Corporation, which buys much of the military research materials.

The sanctioned individuals are Yun Ho-jin, director of Namchongang Trading; Ri Je-son, director of the atomic energy bureau; Hwang Sok-hwa, chief of science at the bureau; Ri Hong-sop, former director of the Yongbyon Nuclear Research Center; and Han Yu-ro, head of another trading company involved in the ballistic missile program.

The goods subjected to a trading ban are a special kind of graphite and a Kevlar filament or tape, which an American official said were used in rockets.