UPDATE 3 - North Korea confirms leader's China trip

ADDS GUTTERES STATEMENT IN GRAPHS 8-9

By Alex Jensen

SEOUL (AA) - North Korea announced Wednesday that its leader, Kim Jong-un, made an "unofficial" visit to China this week, following earlier claims he had travelled abroad for the first time since taking power in 2011.

Media speculation intensified after a special North Korean train arrived Sunday in China amid heavy security.

The North's state-run radio station confirmed Kim was invited by Chinese President Xi Jinping, who reportedly accepted a request to visit the North at his convenience.

Kim was joined by his wife and senior officials, just weeks before planned summits with his counterparts in South Korea and the United States, Moon Jae-in and Donald Trump.

Moon and Trump are aiming to bring about North Korea's denuclearization following years of tensions in the region.

In that regard, Kim's message was positive and in line with talks he held with visiting South Korean officials earlier this month.

"It is our consistent stance to be committed to denuclearization on the peninsula," he was quoted as saying by China's Xinhua News Agency.

UN Secretary General Antonio Guterres welcomed the "reported commitment by the DPRK to denuclearization".

Guterres "views the latest positive developments as the start of a longer process of sincere dialogue, leading to sustainable peace and denuclearization on the Korean Peninsula," his spokesman Farhan Haq said in a statement.

But Kim also insisted South Korea and the U.S. must "respond to our efforts with goodwill, create an atmosphere of peace and stability while taking progressive and synchronous measures for the realization of peace”.

Trump, however, insisted "maximum sanctions and pressure" must remain in place but struck a note of optimism for the pending meeting.

"For years and through many administrations, everyone said that peace and the denuclearization of the Korean Peninsula was not even a small possibility. Now there is a good chance that Kim Jong Un will do what is right for his people and for humanity. Look forward to our meeting!" Trump said on Twitter.

Meanwhile, the South's presidential office was notified by China in advance of Kim's trip, according to an official cited by local news agency Yonhap.

Seoul and Washington had been cagey in response to this week's media speculation, refusing to verify the story.

A White House statement released after Wednesday's confirmation revealed China had also briefed the U.S. on Kim's visit, celebrating the communication as "further evidence that our campaign of maximum pressure is creating the appropriate atmosphere for dialogue with North Korea".

Japanese Premier Shinzo Abe told parliament that he "wants to receive a thorough explanation from China" on Kim's visit.

"At this point, we are in a situation where North Korea is in the process of negotiation. What is important is that North Korea gives up its nuclear and missile programs completely and irreversibly,” Abe said.

Japan’s Chief Cabinet Secretary Yoshihide Suga said sanctions against North Korea should continue until concrete steps are taken.

South Korea’s Foreign Ministry "welcomed" the talks in a written statement.

"The government welcomes Chairman of the State Affairs Commission Kim Jong-un's trip to China from Sunday to Wednesday and his talks with Chinese leaders," the statement said.

"The government hopes that the latest China visit by Chairman Kim, which came ahead of inter-Korean and North-United States summits, will contribute to denuclearizing and building peace on the Korean Peninsula."

* Anadolu Agency correspondent Michael Hernandez contributed to this report from Washington, D.C.