They prepared for days, picking out special dresses or suits, dusting off family photographs, gathering small gifts. They traveled by bus through the snowy countryside and over the demilitarized border into North Korea.

And there, at a mountain resort, a group of elderly South Koreans reunited with relatives they hadn’t seen in six decades. Sisters met brothers. Fathers met daughters. One South Korean was so frail that he entered the ballroom on a stretcher.

The six-day family reunion, which began Thursday, marked a rare show of cooperation between the Koreas, whose governments approved this month a new round of the humanitarian program after a three-year lapse. Although it is unclear whether the reunions will lead to a broader thaw, the resumption signaled that the North Korean government in Pyongyang and the South Korean government in Seoul at a minimum have a shared interest in connecting long-lost relatives, whose separation is one of the enduring sorrows on this divided peninsula.

For many of the South Koreans attending the reunion, this chance to see their relatives is not just their first in decades but is likely to be their last. The 82 participants were chosen by a computer-generated lottery from a waiting list of more than 70,000. The average age of the participants is 84. Many arrived with canes or in wheelchairs accompanied by younger guardians.

“Time is running out for all these elderly people,” said Hong Soon-ho, whose mother, Heo Kyeong-ok, 86, reunited with a younger sister from the North.

Many of the participants, upon seeing their relatives, quivered or fell to the ground. They held hands. They wailed. Eventually, they shared photos and told family stories, in moments captured by South Korean television networks, which broadcast the reunions live. Many of the 180 North Koreans wore traditional colorful dresses called hanboks; all wore state-mandated pins on their left breast. Analysts say North Koreans participating in the reunions are forbidden from talking critically about their totalitarian government.

Two of those representing the North side on Thursday were actually South Koreans; they were fishermen who were abducted by Pyongyang’s agents during the 1970s and have lived in the North since. According to Seoul, more than 500 such South Korean abductees are still in North Korea, prevented from returning home. The North Korean government says that anybody within its borders is there voluntarily.

Before and during the Korean War (1950-53), more than 1 million Koreans criss­crossed the border — a chaotic period in which some family members fled and waited for others to join them. Sometimes they left for financial or ideological reasons. Some wagered that they would find safety on the other side. But a cease-fire then created an impermeable zone in the center of the peninsula, an area strung with barbed wire and dotted with land mines.

Because the war still technically continues — the North and South didn’t sign a treaty — Koreans on both sides are banned from sending mail or making phone calls across the border. Restrictions are particularly strict in the North, where even domestic travel and communication is monitored by state security agents.

In an authoritative report on North Korean abuses released Monday, a United Nations panel recommended that the North allow separated families to unite, “including by allowing citizens to travel or emigrate where they choose.”

During a warmer period of inter-Korean relations, between 2000 and 2010, the North and South held 18 family reunions. They attempted to resume the program last year, but the North called off the event at the eleventh hour. South Korean President Park Geun-hye tried last month to restart negotiations, saying it was time for families to “find healing for their pain.”

This time around, the North accepted and then almost backed out. It was concerned about the upcoming annual South Korea-U.S. joint military exercises, which Pyongyang describes as a prelude to invasion. North and South Korea finally pledged to go ahead with the reunions last week in high-level talks — in spite of the war games.

Yoonjung Seo contributed to this report.