SEOUL, South Korea -- The leaders of South Korea and Japan on Thursday repeated their calls for stronger action to punish North Korea over its nuclear ambitions, including denying the country oil supplies, as they met in eastern Russia.

The demand contradicted the stance of their host, Russian President Vladimir Putin, who in an earlier meeting with South Korean President Moon Jae-in dismissed sanctions as a solution to the country's nuclear and missile development.

Moon and Japanese Prime Minister Shinzo Abe agreed to cooperate on seeking tougher United Nations sanctions against North Korea, which conducted its sixth nuclear test on Sunday in what it claimed was a detonation of a thermonuclear weapon built for missiles capable of reaching the US mainland.

Moon and Abe also pledged to strengthen efforts to persuade Beijing and Moscow into cutting off oil supplies to the North, said Yoon Young-chan, Moon's chief press secretary. Ahead of his meeting with Abe, Moon said that the North's continuing weapons tests have created a "serious and urgent threat unseen before."

In his meeting with Putin in the port city of Vladivostok, Moon urged Moscow to support stronger sanctions against North Korea, but Putin called for talks with North Korea, saying sanctions are not a solution to the country's nuclear and missile development. Putin also expressed concern that cutting off oil supplies would hurt regular North Koreans, Yoon said. Ahead of his meeting with Putin, Moon said the situation could get out of hand if North Korea's missile and nuclear tests aren't stopped.

"We should not give in to emotions and push Pyongyang into a corner," Putin said in a news conference after the meeting, held on the sidelines of a conference on economic development of Russia's Far East. "As never before, everyone should show restraint and refrain from steps leading to escalation and tensions."

Moon, in a phone call with Putin before the conference, also called for a ban on overseas North Korean workers, who are a key foreign currency source for the North. Putin told Moon that the North Korean problem should be solved diplomatically, according to Seoul's presidential office.

Moon took office in May calling for a diplomatic focus, but the torrid pace of North Korea's weapons tests had hardened his government's stance.

Abe, who will meet Putin in Vladivostok on Thursday, said before his departure from Japan that "we must make North Korea understand there is no bright future for the country if it pursues the current path."

Seoul's Defense Ministry on Thursday said the US military has completed adding more launchers to a contentious U.S. missile-defense system in South Korea to better cope with North Korean threats. The deployment of the Terminal High-Altitude Area Defense system has angered North Korea but also China and Russia, which see the system's powerful radar as a threat to their own security.

A Thaad battery normally consists of six launchers that can fire up to 48 interceptor missiles, but only two launchers have been operational so far at the site in rural Seongju.

Several US military vehicles, including trucks carrying payloads covered in black sheets that appeared to be launchers, were seen heading toward a former golf course where the system has been installed.

Dozens were injured earlier as police sent thousands of officers to remove hundreds of protesters from a narrow road leading to the site.

Seonju residents and activists have raised worries over rumored health hazards and the possibility of being targeted by North Korean attacks. (AP)