South Korea's Hyunmoo II ballistic missile is fired during an exercise at an undisclosed location in South Korea. Picture: South Korea Defense Ministry via AP

Beijing/Seoul - The U.S. military staged bombing drills with South Korea over the Korean peninsula and Russia and China began naval exercises on Monday ahead of a U.N. General Assembly meeting this week where North Korea's nuclear threat is likely to loom large.

The flurry of military drills came after Pyongyang fired another mid-range ballistic missile over Japan on Friday and the reclusive North conducted its sixth and most powerful nuclear test on Sept. 3 in defiance of United Nations sanctions and other international pressure.

A pair of U.S. B-1B bombers and four F-35 jets flew from Guam and Japan and joined four South Korean F-15K fighters in the latest drill, South Korea's defence ministry said.

The joint drills were being conducted "two to three times a month these days", Defence Minister Song Young-moo told a parliamentary hearing on Monday.

Earlier on Monday, the official Xinhua news agency in Beijing said China and Russia began naval drills off the Russian far eastern port of Vladivostok, not far from the Russia-North Korea border.

Those drills were being conducted between Peter the Great Bay, near Vladivostok, and the southern part of the Sea of Okhotsk, to the north of Japan, it said.

The drills are the second part of China-Russian naval exercises this year, the first part of which were staged in the Baltic in July. The Xinhua report did not directly link the drills to current tensions over North Korea.

China and Russia have repeatedly called for a peaceful solution and talks to resolve the issue.

On Sunday, however, U.S. Ambassador to the United Nations Nikki Haley said the U.N. Security Council had run out of options on containing North Korea's nuclear programme and the United States might have to turn the matter over to the Pentagon.

In response, Chinese Foreign Ministry spokesperson Lu Kang said the most pressing task at present was for all parties to enforce the latest U.N. resolutions on North Korea fully rather than "deliberately complicating the issue".

Military threats from various parties have not promoted a resolution to the issue, he said.

"This is not beneficial to a final resolution to the peninsula nuclear issue," Lu told a daily news briefing.

U.S. President Donald Trump has vowed that North Korea will never be able to threaten the United States with a nuclear-tipped ballistic missile.

Asked about Trump's warning last month that the North Korean threat to the United States would be met with "fire and fury", Haley said: "It was not an empty threat."

Washington has also asked China to do more to rein in its neighbour and ally, while Beijing has urged the United States to refrain from making threats against the North.

The U.N. Security Council unanimously passed a U.S.-drafted resolution a week ago mandating tougher new sanctions against Pyongyang that included banning textile imports and capping crude and petrol supply.

Gasoline and diesel prices in the North have surged since the latest nuclear test, according to market data analysed by Reuters on Monday.

Japanese Prime Minister Shinzo Abe said in an editorial published in the New York Times on Sunday the international community must remain united and enforce sanctions against North Korea after its repeated launch of ballistic missiles.

Such tests were in violation of Security Council resolutions and showed that North Korea could now target the United States or Europe, he wrote.

Abe also said diplomacy and dialogue would not work with North Korea and concerted pressure by the entire international community was essential to tackle the threats posed by the north and its leader, Kim Jong Un.

However, the official China Daily argued on Monday that sanctions should be given time to bite and that the door must be left open to talks.

"With its Friday missile launch, Pyongyang wanted to give the impression that sanctions will not work. Some people have fallen for that and immediately echoed the suggestion, pointing to the failure of past sanctions to achieve their purpose," it said in an editorial.

"But that past sanctions did not work does not mean they will not. It is too early to claim failure because the latest sanctions have hardly begun to take effect. Giving the sanctions time to bite is the best way to make Pyongyang reconsider," the newspaper said.

Pyongyang has launched dozens of missiles as it accelerates a weapons programme designed to provide the ability to target the United States with a powerful, nuclear-tipped missile.

It says such programmes are needed as a deterrent against invasion by the United States, which has 28 500 troops stationed in South Korea. On Saturday, it said it aimed to reach an "equilibrium" of military force with the United States.

The United States and South Korea are technically still at war with North Korea because the 1950-53 Korean conflict ended with a truce and not a peace treaty.