North and South Korea wrapped up Tuesday their first reunion for divided families in more than three years, an event that raised hopes of a sustainable improvement in volatile cross-border ties.

More than 350 South Koreans said a final farewell to 88 North Korean relatives, concluding a second round of meetings for those separated by the 1950-53 Korean War.

A North Korean patrol boat repeatedly crossed the disputed Yellow Sea border with the South in an apparent show of force at the start of South Korea-U.S. military drills, Seoul's defense ministry said Tuesday.

The incursion took place three times overnight Monday and at one point the North Korean naval vessel had reached two nautical miles inside the South side of the border.

South Korea kicked off its annual joint military exercises with the United States on Monday, despite vocal opposition from North Korea which could threaten a recent upswing in cross-border ties.

The start of this year's drills overlaps with the first reunion for more than three years of families divided by the Korea War -- an event that has raised hopes of greater North-South cooperation.

A second group of South Koreans met North Korean relatives Sunday at a reunion for families divided for decades, a day before South Korean-US military exercises that threaten to sour relations.

The reunion -- held at the North's Mount Kumgang resort from last Thursday till this Tuesday -- is the first in more than three years for families torn apart by the 1950-53 Korean War.

North Korea on Friday "categorically" rejected a U.N. report on its human rights record, accusing it of being a "sheer fabrication" invented by the United States and its allies.

A U.N. report released Monday said North Korea's leaders should be brought before an international court for a litany of crimes against humanity.

The joy of being reunited for the first time in decades turned to grief for North and South Korean families Saturday as a rare cross-border visit ended, with participants unlikely to see their relatives again.

In perhaps the most traumatic moment of the emotionally-charged event, 80 elderly South Koreans and their 174 Northern relatives were separated, many at first refusing to let go of their loved ones' hands.

Around 80 elderly South Koreans met privately Friday with North Korean relatives they haven't seen for 60 years, on the second day of a highly-charged reunion for families divided by the Korean War.

In contrast to the previous day when their tearful and, in some cases, clearly traumatic meetings were played out in front of TV cameras, they were allowed three hours in their own rooms to try and bridge the decades of separation.

A group of 82 elderly and frail South Koreans held an emotional reunion Thursday with family members in North Korea, more than 60 years after they were separated by the Korean War.

The first North-South family reunion for more than three years began around 3:00pm (0600 GMT) with a mass gathering in the main hall of a resort on North Korea's Mount Kumgang, a Unification Ministry official said in Seoul.

U.N. chief Ban Ki-moon said Tuesday he was "deeply disturbed" by findings of "grave" human rights violations in North Korea from a U.N.-mandated inquiry, saying he hoped the report would raise international awareness.

The detailed and wide-ranging report, compiled by the Commission of Inquiry (COI) on North Korea, offers a searing indictment of Pyongyang's rights record, detailing murder, enslavement, torture, imprisonment, rape, forced abortions and other sexual violence.

Beijing on Tuesday dismissed a U.N. report's warning that its officials could be complicit in alleged human rights violations by Pyongyang by forcibly repatriating North Koreans from China.

A 400-page United Nations report issued Monday detailed human rights violations including "extermination, murder, enslavement, torture, imprisonment, rape, forced abortions and other sexual violence".