Two North Korean soldiers stand guard in front of the Unha-3 rocket at Tangachai -ri space center on April 8, 2012. North Korea has confirmed their intention to launch the rocket next week despite international condemnations. (Pedro Ugarte/AFP/Getty Images)

As North Korea prepares for a long-range rocket launch within the next week, the South Korean government has released fresh evidence that, it says, suggests a nuclear test soon could follow.

Seoul’s Ministry of Unification, in charge of policy toward Pyongyang, on Sunday sent a report to journalists detailing activity at a test site in North Korea’s northeast, the location for previous nuclear tests in 2006 and 2009. The report, citing recent commercial satellite images, said that the North is “on its way to another grave provocation” by gathering dirt at the entrance to a tunnel.

According to the analysis, that dirt would be used to plug the tunnel before conducting an underground test, which would be the North’s third.

“The effort is believed to be in its final stages,” said the report, which was drafted by Seoul’s intelligence agency. “The soil around the tunnel’s entrance appeared to have been brought in from another region and has been growing in amount since March.”

If North Korea conducts a nuclear test soon after launching its rocket, it would match the pattern set by the reclusive country in 2006 and 2009, in which launches brought international condemnation. In both cases, Pyongyang, outraged by the outrage, tested nuclear devices soon after.

But predictions about a third nuclear test have run rampant in the past two years, and progressive media in Seoul suggested that the latest release was an attempt by the ruling conservative party to gain voter support in advance of Wednesday’s parliamentary elections.

The announcement might be a “red herring election move by conservatives,” the liberal Hankyoreh newspaper said in a headline on its Web site.

North Korea conducted its previous nuclear tests in October 2006 and May 2009. After both tests, the United Nations Security Council passed sanctions designed to isolate Pyongyang and prevent it from future provocative actions. The 2009 sanctions specifically demanded that North Korea “not conduct any further nuclear test or any launch using ballistic missile technology” — technology that U.S. officials say will be used in the upcoming rocket launch.

The North has maintained that the three-stage rocket launch is intended to put a satellite into orbit. But officials in Washington, Seoul and Tokyo fear the launch is a cover for Pyongyang to test its ballistic missile technology.

Just weeks before Pyongyang announced its intentions to conduct the launch, it agreed to a deal with Washington in which the U.S. would deliver food aid in exchange for a halt on weapons tests and a freeze on parts of its nuclear program.

If the North goes ahead with the launch, President Obama said last month, the authoritarian country will likely face a new round of sanctions. It would be “difficult,” Obama said, “to move forward with that [food] package if they show themselves unable to [keep] commitments that they’ve made even a month earlier.”

The North’s planned launch is timed to mark the centennial celebration of founder Kim Il Sung’s birth. Pyongyang says it has the right, under an international space treaty, to launch a satellite for peaceful purposes; the isolated country granted visas to select foreign journalists to cover the event. On Sunday, those journalists received a tour of the launch station in the northwestern corner of the country, near the Chinese border.

The satellite, the North’s state-run news agency said, “will gather necessary information on the distribution of forestry resources in the country, severity of natural disasters, crop estimate, weather forecast and survey of natural resources during polar orbit.”

Some Asian airlines — Philippine Airlines, Japan Airlines and All Nippon Airways — plan to change flight paths to avoid the rocket, the Associated Press reported.

Special correspondent Yoonjung Seo contributed to this report.