South Korean President Moon Jae-in has told Russian leader Vladimir Putin the situation on the Korean peninsula could become unpredictable if Pyongyang did not halt its "provocative actions" after its latest nuclear bomb test.
Putin and Moon met on the sidelines of an economic summit in the far eastern Russian city of Vladivostok amid mounting international concerns that their shared neighbour plans more weapons tests, possibly a long-range missile launch ahead of a key weekend anniversary.
Moon, who came to power earlier this year advocating a policy of pursuing engagement with Pyongyang, has come under increasing pressure to take a harder line on North Korea.
He said the United Nations should consider tough new sanctions on North Korea, including halting oil shipments, after Sunday's nuclear test.
However, Putin said it was not possible to resolve the North Korean crisis with just sanctions and pressure alone.
"Pyongyang's missile and nuclear program is a crude violation of UN Security Council resolutions, undermines the non-proliferation regime and creates a threat to the security of northeastern Asia," Putin said at a joint news conference.
"At the same time, it is clear that it is impossible to resolve the problem of the Korean peninsula only by sanctions and pressure.
"Without political and diplomatic tools, it is impossible to make headway in the current situation; to be more precise, it is impossible at all."
Putin on Tuesday described sanctions it as a "road to nowhere" with North Korea.
Sanctions have so far done little to stop North Korea boosting its nuclear and missile capacity as it faces off with US President Donald Trump, who has vowed to stop Pyongyang from being able to hit the US mainland with a nuclear weapon.
US Ambassador to the United Nations Nikki Haley accused North Korean leader Kim Jong Un on Monday of "begging for war" with a series of nuclear bomb and missile tests. She urged the 15-member Security Council to impose the "strongest possible" sanctions to deter him and shut down his trading partners.
Japanese Prime Minister Shinzo Abe, who will discuss North Korea with Moon and Putin in Vladivostok, said on Wednesday he wanted the North to understand it has "no bright future" if it continues on its current path.
A top North Korean diplomat warned on Tuesday his country is ready to send "more gift packages" to the United States. South Korea's Unification Ministry said on Wednesday it was still expecting more activity from the North.
Han Tae Song, Pyongyang's ambassador to the United Nations in Geneva, confirmed that North Korea had successfully conducted its sixth and largest nuclear bomb test on Sunday.
"The recent self-defence measures by my country, DPRK, are a gift package addressed to none other than the US," Han told a disarmament conference, using the acronym for North Korea's formal name, the Democratic People's Republic of Korea.
"The US will receive more 'gift packages' ... as long as it relies on reckless provocations and futile attempts to put pressure on the DPRK," he said without elaborating.
Sunday's test of what North Korea said was an advanced hydrogen bomb was its largest by far.
Japan upgraded its assessment of the North Korean test to 160 kilotons from 120 kilotons after the size of the earthquake it generated was revised to 6.1.
Satellite imagery appeared to show the blast caused numerous landslides at North Korea's Punggye-ri test site, according to 38 North, a Washington-based North Korean monitoring project.
