North Korea and Japan wrapped up three days of talks in Stockholm on Wednesday, agreeing to continue their dialogue on Japanese nationals abducted decades ago by Pyongyang.

The meeting at a hotel in the Swedish capital, which saw the exchange of "tough words" at times, came after the two countries held their first official talks in 16 months in Beijing in March.

North Korea and Japan began Tuesday the second day of talks in Stockholm believed to be focused on Japanese nationals kidnapped decades ago by Pyongyang.

Japan is expected to push for a reopening of the investigation into the fate of the abductees, kidnapped in the 1970s and 1980s to train North Korean spies.

North Korea on Tuesday warned that recent "provocative" activities by U.S. troops at a truce village on the heavily fortified inter-Korean border could lead to a "catastrophic" military clash.

The warning came from the head of the North Korean forces stationed in the frontier village of Panmunjom -- where the ceasefire agreement to end fighting in the 1950-53 Korean War was signed.

North Korea and Japan wrapped up a first day of talks in Stockholm Monday, with the fate of Japanese nationals kidnapped decades ago by Pyongyang said to top the agenda.

The three days of meetings in the Swedish capital take place after the two countries held their first official talks in 16 months in China in March, addressing a range of subjects including the abduction issue, recent missile launches and North Korea's nuclear weapons program.

North Korea and Japan are expected to discuss the fate of Japanese nationals kidnapped decades ago by Pyongyang as their envoys meet for three days of talks in Stockholm from Monday.

The meeting in the Swedish capital takes place after the two countries held their first official talks in 16 months in China in March, speaking on a range of issues including the abduction issue and North Korea's nuclear weapons program.

A U.S. surveillance drone arrived at an air base in northern Japan on Saturday for the first deployment of the spy aircraft in the country, the U.S. Air Force said.

The Global Hawk was brought to the U.S. Misawa Air Base from Guam "to support U.S. intelligence, surveillance, and reconnaissance missions and contingency operations throughout the Pacific theater," America's air force said on its website.

Pentagon chief Chuck Hagel will embark Wednesday on a 12-day trip that will take in Singapore before heading to Europe for talks with NATO allies.

The tour will begin with a brief stop at Joint Base Elmendorf-Richardson in Alaska, where the U.S. defense secretary will receive briefings on missile defense, his office said.

Seoul Friday accused North Korea of a "blatant lie" in claiming it had not fired shells near a South Korean warship and said Pyongyang had threatened to bombard its military vessels.

The North's military earlier Friday had rejected as "sheer fabrication" Seoul's assertion that it fired two shells in the vicinity of a South Korean navy vessel on patrol near the tense sea border Thursday.

North Korea on Thursday fired shells into waters near a South Korean warship on patrol south of the disputed Yellow Sea border, prompting an evacuation of residents on a nearby island, officials said.

Two shells fell near the South Korean ship, which was sailing near the frontline island of Yeonpyeong, the South's defense ministry said.

North Korea threatened Wednesday to launch an attack on South Korean warships without warning if there was even a "trifling" provocation near their disputed Yellow Sea border.

A South Korean naval ship fired warning shots Tuesday after three North Korean patrol boats crossed the sea boundary.