Chinese state media coverage of the Korean peninsula shelling incident avoided criticising Beijing's close ally Pyongyang on Wednesday and even said the episode showed North Korea's "toughness".

North Korea fired a deadly barrage of artillery shells onto a South Korean island on Tuesday in one of the most serious border incidents since the 1950-1953 war, sparking global condemnation of Pyongyang.

China's official response has so far been relatively tepid, however, while state media have largely avoided pointing the finger at North Korea and taken an occasionally pro-Pyongyang tone.

"North Korea showed its toughness during the skirmish," the Global Times said in an editorial that also criticised the "failure of the hard-line policies" of the current South Korean government toward its northern neighbour.

Amid growing pressure for Beijing to rein in its close ally, China's only official response has come from a government spokesman who on Tuesday expressed "concern", while saying Beijing sought to "verify" what took place.

Chinese news accounts of the shelling, which provoked retaliatory South Korean fire, also refrained from assigning blame but highlighted North Korean claims that South Korea triggered the exchange.

A report in the People's Daily, the Communist Party's print mouthpiece, led off with Pyongyang's assertion that Seoul suddenly began bombarding North Korean territory in a "reckless military provocation".

A front-page subheading on the English-language China Daily read: "DPRK accuses ROK of firing first," using the acronyms for the official names of North and South Korea.

Coverage of the incident on China Central Television, the Communist government's main broadcast mouthpiece, included prominent play for a North Korean news broadcast railing at South Korea and threatening retaliation.

The official Xinhua news agency, meanwhile, questioned how the exchange of fire started.

"Though Seoul blamed Pyongyang for military provocations, there is still no way to confirm who started the shelling attack," it said in a report on the United States and South Korea agreeing to hold joint military exercises soon.

China avoids criticising North Korea despite numerous provocations over the years by Pyongyang.

Experts say Beijing's approach is guided by a desire to prop up the regime of Kim Jong-Il out of fear that its collapse could spark a flood of refugees into China.

It also wants to check US influence in the region, and fears that an eventual unified Korean peninsula would be dominated by South Korea's US-allied government.

China also refrained from joining world condemnation of North Korea after it was blamed for a torpedo attack on the South Korean Cheonan naval ship earlier this year that killed 46 sailors.

It refused to endorse the findings of an international panel that said North Korea was to blame, saying it would instead conduct its own inquiry. But it has given no updates on any results from its probe.