China appealed for "calm and restraint" on the Korean peninsula on Wednesday, after North Korea blocked South Korean entry to a key joint industrial zone at Kaesong.
Pyongyang's move was the latest in a cycle of escalating tensions since it fired a long-range rocket in December and conducted its third nuclear test in February.
"Under the current circumstances China believes that all parties should exercise calm and restraint," foreign ministry spokesman Hong Lei told reporters at a regular briefing, repeating Beijing's oft-declared position.
Vice-minister Zhang Yesui had met North Korea's ambassador on Tuesday, and those of South Korea and the United States, to express "serious concern over the situation in the peninsula", added Hong.
China urged that all sides "do not take provocative actions and should not take actions that would worsen the situation", he said. "We hope all parties look at the long term, engage in dialogue and improve their relations."
Beijing has been Pyongyang's sole major ally for decades and is its biggest trading partner, providing key energy supplies to the poverty-stricken nation.
Tensions on the peninsula have soared in over the past week, with Pyongyang announcing it would restart a nuclear reactor to feed its nuclear weapons programme.
On Friday it ordered missile units to standby, hours after nuclear-capable US B-2 stealth bombers were deployed in US joint military drills with South Korea.
Any move on the Seoul-funded Kaesong complex -- set up in 2004 and a vital source of hard currency for North Korea -- carries tremendous significance and the potential to send tensions mounting further.
Neither of the Koreas has allowed previous tensions to significantly affect Kaesong, the only surviving example of inter-Korean cooperation and seen as a bellwether for the stability of the peninsula.
The US on Tuesday called on China to do more to rein in North Korea, with White House spokesman Jay Carney telling reporters: "It is not a mystery to anyone that China has influence with North Korea.
"We have in the past and are now urging China to use that influence to try to affect North Korean behaviour."