China issued a stern warning Friday that a conflict over North Korea could break out “at any moment”, as Pyongyang vowed a “merciless” response to any US military action.

Tensions in the region have surged to fresh heights in recent days with speculation mounting that the North is preparing a sixth nuclear test.

A US naval strike force has been deployed near the Korean peninsula, and President Donald Trump has issued stark warnings that the threat posed by Pyongyang's nuclear weapons programme “will be taken care of”.

A clearly rattled China, under pressure from Trump to prevent any North Korean provocation, said the situation had reached breaking point.

“One has the feeling that a conflict could break out at any moment,” Chinese foreign minister Wang Yi said.

“If a war occurs, the result is a situation in which everybody loses and there can be no winner,” he added during a joint press conference in Beijing with the visiting French foreign minister.

Wang's comments mirrored a warning from the North Korean foreign ministry's Institute for Disarmament and Peace that “thermo-nuclear war may break out any moment”.

Atomic jitters

North Korea has invoked similarly dire scenarios on previous occasions when tensions on the Korean peninsula have spiked, but Beijing's warnings have fuelled international concerns that the current situation is reaching tipping point.

The North's Korean People's Army (KPA) added its voice to the bellicose rhetoric on Friday with a statement threatening strikes against US military bases and other targets in South Korea.

“The closer such big targets as nuclear powered aircraft carriers come, the greater would be the effect of merciless strikes,” said the statement carried by the North's official KCNA news agency.

Citing the recent missile strike Trump ordered against Syria - which was widely interpreted as a warning to Pyongyang - the KPA denounced the US president for embarking on a path of “open threat and blackmail” against the North.

It also urged Washington to “come to its senses” and find a “proper” solution to the current stand-off.

Trump's military muscle-flexing was on display again Thursday when the US on dropped the biggest non-nuclear bomb it possesses on Afghanistan, targeting a complex used by the militant Islamic State group.

The American president has repeatedly said he will prevent Pyongyang from its goal of developing a nuclear-tipped ballistic missile capable of reaching the mainland United States.

A White House foreign policy advisor said Friday that the US was assessing military options, and added that another provocative test was a question of “when” rather than “if.”

Satellite imagery analysis has noted activity at the North's main nuclear test site ahead of Saturday's 105th anniversary of the birth of the country's founder leader Kim Il-Sung.

Spotlight on China

The North's sabre-rattling has encouraged a rapprochement between Trump and his Chinese counterpart Xi Jinping, who met face-to-face for the first time late last week at Trump's Mar-a-Lago resort.

Though his election campaign was marked with acerbic denouncements of China's “rape” of the US economy, Trump dropped his anti-China bombast in Florida, afterwards hailing an “outstanding” relationship with Xi.

But he insists China - the North's sole major ally and economic lifeline - must exert more leverage on Pyongyang to abandon its nuclear ambitions or suffer the consequences.

Beijing has long opposed dramatic action against the North, fearing the regime's collapse would send a flood of refugees across its borders and leave the US military on its doorstep.

China's state broadcaster CCTV announced Friday that Air China - the only foreign carrier operating commercial flights into North Korea - would suspend services to Pyongyang from next week.

The report gave no reason for the suspension, but noted that Air China has taken similar action in the past because of low passenger volumes.

Despite the mounting tensions, there has been little sign of strain on the streets of Pyongyang in recent days, where the focus has been on preparations for Saturday's anniversary.

North Korean leader Kim Jong-Un on Thursday unveiled the sprawling Ryomyong street development, a prestige housing project repeatedly promised in time to mark the occasion.

Before the international press and tens of thousands of his adoring citizens, he cut a wide red ribbon to rhythmic cheers, before waving and returning to his Mercedes limousine.