China urges caution and opposes moves that increase tension.
The United States and its allies may boost their military presence in the Asia-Pacific region, citing Pyongyang's nuclear test, analysts said.
The comments came as China engaged in a flurry of diplomacy on Wednesday to ease regional tension.
"More drills by the US and its allies are possible in a bid to show their firm opposition to the nuclear test and other measures by Pyongyang they call provocative," said Wang Fan, an expert on Korean studies at the China Foreign Affairs University.
They will also quicken deployment of anti-missile systems in the name of containing the Democratic People's Republic of Korea, Wang said.
Washington, Seoul and Tokyo on Wednesday agreed to deepen cooperation to curb Pyongyang.
The DPRK conducted its third nuclear test on Tuesday in what its officials described as a "safe and perfect" way.
China held talks on Wednesday with countries involved in the Six-Party Talks.
Foreign Minister Yang Jiechi and his Republic of Korea counterpart Kim Sung-hwan talked over the phone and exchanged their views on the situation on the Korean Peninsula, the Foreign Ministry said on its website, without giving details.
Yang also talked with US Secretary of State John Kerry. Yang told Kerry that China explicitly stated its position on Pyongyang's nuclear test, urging all parties to keep focused and avoid escalation, according to the ministry.
All parties concerned should insist on a peaceful solution, resolve the Korean Peninsula issue within the framework of the Six-Party Talks, and maintain peace and stability on the peninsula and in Northeast Asia, Yang said.
On Tuesday, China said it firmly opposed the test.
The ROK president-elect, Park Geun-hye, on Wednesday condemned Pyongyang's test, saying "a stronger nuclear arsenal means deeper international isolation".
Even if the DPRK conducts its fourth and fifth nuclear tests, that will never increase its negotiating power, she said. Only when Pyongyang tries to abandon its nuclear weapons can its negotiating power rise, she added.
The ROK military said on Wednesday Seoul has deployed missile systems covering the whole territory of the DPRK, to cope with Pyongyang's nuclear threats, according to the Yonhap news agency.
The agency cited a Seoul foreign ministry official as saying that Seoul's countermeasures focus on how to limit the money, technology and spare parts which Pyongyang's nuclear test requires, but will not include military means.
Ruan Zongze, vice-president of the China Institute of International Studies, said Seoul needs to soothe domestic worries over the DPRK's nuclear test.
Wang, from the China Foreign Affairs University, said Seoul's military countermeasures will help Washington and its allies strengthen their military power in the region.
Leaders of the US, Japan and the ROK discussed the nuclear issue over the phone.
US President Barack Obama guaranteed ROK President Lee Myung-bak that the US will offer protection to the ROK to cope with possible DPRK threats, according to Yonhap.
This shows that the US may use Pyongyang's test as an excuse to push for military deployment in East Asia, a scenario that will only increase regional tension, Ruan said.
The UN Security Council had an emergency meeting on Tuesday in New York.
"The members of the Security Council will begin work immediately on appropriate measures in a Security Council resolution," the council said in a statement.
Bruce Klingner, a senior research fellow for Northeast Asia at the Heritage Foundation in Washington, said the DPRK had again defied the UN and recent efforts by China to prevent its neighbor from ratcheting up tension.
'No health impact'
Pyongyang's nuclear test has not had a negative impact on China's environment or public health, the Ministry of Environmental Protection said on Wednesday.
Readings from 25 monitoring stations, on and near the border, were at normal levels by 10 am, it said. The test site is about 100 km away from the border.
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