TOKYO — North Korea on Wednesday successfully fired into orbit a long-range rocket carrying a satellite, an outside aerospace monitoring organization said, a major advance in the authoritarian nation’s weapons program.

According to the North American Aerospace Defense Command, a joint organization of the United States and Canada, North Korea “deployed an object that appeared to achieve orbit” after the first and second stages of the rocket dropped into the sea.

Based on that assessment, the third stage of the rocket, as well as the satellite, would have entered orbit, aerospace experts said.

Though the Unha-3 rocket did not carry a warhead, it relied on technology similar to that of a long-range missile, leading Washington, Seoul and Tokyo to describe the launch as a de facto missile test that violated U.N. Security Council resolutions.

The North also said Wednesday that its launch was a success.

If North Korea indeed placed a satellite into orbit, it would mark a significant breakthrough in its decades-long attempt to develop an intercontinental ballistic missile capable of hitting the United States and would present a new threat for the Obama administration.

The North had carried out four previous missile or rocket launches, dating back to 1998. In the most recent one, eight months ago, the rocket broke apart after roughly 90 seconds and dropped into the sea.

The rocket launched Wednesday was fired from a facility in the country’s northwestern corner, not far from the Chinese border. It traveled southward, zipping over the water between South Korea and China, flying above the Japanese island of Okinawa, then heading toward the Philippines.

According to the Japanese government, stages of the rocket fell into the Yellow Sea and the East China Sea, the planned trajectory that North Korea had described in its report to the International Maritime Organization, which is responsible for maritime safety.

South Korean President Lee Myung-bak called an emergency security meeting, and a Japanese government spokesman called the launch “unacceptable.”

“It is extremely regrettable that North Korea went through with the launch despite our calls to exercise restraint,” said the spokesman, Osamu Fujimura.

China also expressed its unhappiness with the long-range launch. Foreign Ministry spokesman Hong Lei told reporters: “We express regret at (North Korea’s) launch in spite of the extensive concerns of the international community.”

Hong said China “believes U.N. Security Council reaction should be prudent and moderate and conducive to maintaining stability and avoiding escalation of the situation.”

In Washington, the White House called the launch a “highly provocative act that threatens regional security.”

Rep. Ileana Ros-Lehtinen (R-Fla.), chairman of the House Foreign Affairs Committee, criticized the launch, saying it shows that a defiant Pyongyang “is moving ever closer towards its ultimate goal of producing a nuclear ballistic missile.”

The launch caught North Korea’s neighbors off guard. Though the North had stated earlier this month that it would go ahead, South Korean military officials on Tuesday told reporters in Seoul that Pyongyang was disassembling its rocket to fix technical problems.

The rocket was launched at 9:51 a.m. local time, according to the South Korean government.

For North Korea, an impoverished, authoritarian police state, the launch comes at a critical time. The country is days away from the one-year anniversary of the death of leader Kim Jong Il, and some outside analysts called the rocket blast a means to mark the occasion. The launch also comes just eight months after the high-profile failure — one the North had invited foreign journalists to watch.

After that rocket, also named Unha-3, broke apart seconds after liftoff, the North — in a rare moment of transparency — admitted to its people what had happened.

This time, North Korea told its citizens almost nothing.. Though the government had laid out its plans on its state news agency Web site, only the most elite North Koreans have access to the Internet. The North never mentioned the plans in its newspaper, the Rodong Sinmun.

But Wednesday, roughly two hours after the rocket lifted off, the North held a special noon television broadcast, which opened with martial music and a picture of national founder Kim Il Sung.

The blast also comes one week before South Korea’s presidential election. National security and relations with the North have been lower priorities in the race compared with domestic economic issues. But the North’s announcement — and the launch Wednesday — placed a greater spotlight on the dangers posed by a family-run government that funnels its money to weapons programs.