N.Korea an 'unprecedented threat' says Mattis and Pacific allies

US Secretary of Defense James Mattis and his Asian counterparts vowed to step up diplomatic pressure on Pyongyang while enhancing military cooperation

North Korea's weapons programmes pose "an unprecedented and grave threat" to the United States, South Korea and Japan, defence ministers from the three countries warned Tuesday.

US Secretary of Defense James Mattis and his Asian counterparts vowed to step up diplomatic pressure on Pyongyang while enhancing military cooperation as they held security talks in the Philippines.

Tension has been high on the divided Korean peninsula for months with Pyongyang staging its sixth nuclear test and launching two ICBMs that apparently brought much of the US mainland into range.

"The three ministers condemned, in the strongest terms, North Korea's continued provocative actions," read a joint statement from Mattis, Japanese defence minister Itsunori Onodera and South Korean defence minister Song Young-Moo.

"The ministers called on North Korea to abandon its unlawful nuclear and ballistic missile programmes in a complete, verifiable, and irreversible manner."

The allies also pledged to enforce United Nations sanctions against the North, and expand information sharing.

Mattis is on an Asian tour which will see him visiting Seoul for annual defence talks -- ahead of a visit to South Korea by Donald Trump.

All eyes will be on Trump's message to Pyongyang after the US president and the North's leader Kim Jong-Un have traded threats of war and personal insults.

Trump's recent remark that "only one thing will work" with North Korea fuelled concerns of a potential conflict.

But even some White House advisers say US military options are limited when Pyongyang could launch an artillery barrage on the South Korean capital Seoul -- only around 50 kilometres (30 miles) from the heavily fortified border and home to 10 million people.

Mattis also met counterparts from the 10-member Association of Southeast Asian Nations who are gathering for talks in the northern Philippine city of Clark.

The Pentagon said the US defence chief and ASEAN ministers discussed North Korea as well as the "the need to increase cooperation on countering violent extremism to stem the threat posed from groups" such as the Islamic State and "the threat posed by returning foreign fighters".

A five-month battle against Islamic State supporters in the southern Philippines that claimed more than 1,100 lives ended following a final battle inside a mosque, Manila said on Monday.

The conclusion of the conflict ended immediate fears that IS would establish a Southeast Asian base in the southern city of Marawi.

However, concerns remain about its longer-term intentions and capabilities in the region.