Hundreds of thousands of North Korean soldiers and civilians rallied Friday in the center of Pyongyang for a mass celebration of the country's long-range rocket launch, state television showed.

The huge crowd in Kim Il-Sung Square, standing in neat, organised ranks, applauded speeches by senior military, party and government officials hailing the success of Wednesday's launch and praising the country's young leader, Kim Jong-Un.

South Korea's navy has launched a salvage operation in the Yellow Sea to retrieve debris from North Korea's long-range rocket launch, military officials said Thursday.

The first stage of the North's Unha-3 rocket launched on Wednesday fell in the sea off the Korean peninsula, while the second splashed down east of the Philippines.

The United States on Wednesday demanded "consequences" for North Korea's rocket launch and said it would seek international action in coming days.

U.S. ambassador to the United Nations Susan Rice said the North's launch "shows that despite the Security Council's clear requirements, North Korea is determined to pursue its ballistic missile program without regard for it international obligations.

The U.N. Security Council, including China and the United States, on Wednesday condemned North Korea for carrying out a banned rocket launch and warned it could take further action.

"Members of the Security Council condemned this launch which is a clear violation of Security Council resolutions 1718 and 1874," said a statement by the 15-nation body after emergency consultations.

Iran congratulated North Korea on Wednesday for its "successful" launch of a long-range rocket, an incident which provoked global condemnation, and denied having a role in preparing the launch.

Tehran "congratulates the people and the government" of North Korea on "the successful launching of the satellite-carrying rocket," Iran's armed forces deputy chief, Brigadier General Masoud Jazayeri, told the Fars news agency.

The European Union threatened fresh sanctions against North Korea Wednesday, condemning its long-range rocket launch as a violation of international law.

"The EU will consider an appropriate response, in close consultation with key partners... including possible additional restrictive measures," foreign policy chief Catherine Ashton said in a statement.

China's foreign ministry said Wednesday it regretted North Korea's long-range rocket launch, echoing a similar reaction from Russia and following strong condemnation from the United States.

"We express regret at the Democratic People's Republic of Korea's launch in spite of the extensive concerns of the international community," China foreign ministry spokesman Hong Lei told reporters.

North Korea successfully launched on Wednesday a long-range rocket, which U.N. chief Ban Ki-moon and the U.S. said was a "provocative act" in clear breach of U.N. Resolutions.

The launch triggered plans for an emergency session of the Security Council, which has imposed round after round of sanctions against North Korea over its ballistic missile and nuclear programs, so far to little avail.

Iran on Tuesday denied a South Korean report that its missile experts were in North Korea offering technical assistance for the planned launch of a long-range rocket.

"This issue is utterly not true," Ramin Mehmanparast, foreign ministry spokesman told reporters.

North Korea has removed a section of its long-range rocket, a report said Tuesday, a day after Pyongyang extended the launch window for the widely-criticized mission due to technical problems.

Satellite images taken on Monday showed signs that technicians had begun to "disassemble part of the rocket" at the Sohae satellite launch center, Yonhap news agency quoted a government source as saying.