South Korea said Monday that the country and the United States are tightening surveillance as the Democratic People's Republic of Korea (DPRK) proceeds with its rocket launch plan, officials here said Monday.

Last month, the DPRK announced the plan to launch an "earth observation" satellite between April 12 and 16 to mark the 100th anniversary of the birth of DPRK founder Kim Il Sung.

But South Korea and the United States insist that the launch will be a disguised long-range ballistic missile test that breaches a United Nations ban.

"South Korea and the United States are keeping close tabs on movements related to North Korea (DPRK)'s long-range missile launch," a Joint Chief of Staff official told reporters at a briefing earlier in the day. "At the moment, we are strengthening surveillance."

The South Korean military is "fully prepared" to respond to any acts of provocations, the official added, on condition of anonymity.

The remarks came a day after a group of some 70 foreign journalists were invited to visit the Sohae Satellite Launching Station in the DPRK's northwest and take a look at the 30-meter high Unha-3 rocket that would carry the Kwangmyongsong-3 satellite into the space.

"It is a carrier rocket but not a ballistic missile," Jang Myung Jin, who is in charge of the station, told reporters. He added that the launch is a peaceful program aimed at developing the DPRK's economy and raising the people's living standard.

While Jang said the launch will "not affect" other countries in the region, South Korea has said it might shoot down the rocket if it strays into its territory.

The DPRK has warned of "merciless punishment" for such attempts.

China has expressed its concern about the development of the situation and called on all parties concerned to take a broad and long-term perspective, remain calm and exercise restraint, and seek proper solutions to the relevant issues through diplomatic channels and by peaceful means.

"China will maintain close communication and coordination with the relevant parties and work with them to play a constructive role in upholding overall peace and stability of the region and advancing the Six-Party Talks process," said Chinese Foreign Minister Yang Jiechi Sunday while meeting his Japanese and South Korean counterparts on trilateral cooperation in Ningbo, a coastal city of China's Zhejiang province.