Dozens of elderly North and South Koreans separated for six decades have been reunited during a rare period of detente between the rival Koreas. The reunions are all the more poignant because the participants will part again in a few days, possibly for ever.

About 80 South Koreans travelled through snow with their families to North Korea's Kumgang Mountain resort to meet children, brothers, sisters, spouses and other relatives. Seoul had said about 180 North Koreans were expected.

South Korean television showed women in brightly coloured traditional hanbok dresses talking and hugging, and families exchanging photographs of relatives who couldn't attend or had died. Two brothers grasped each other and pressed their foreheads together as cameras flashed.

South Korean Park Yang-gon, left, meets with his North Korean brother Park Yang-soo. Photograph: Pool/Getty Images

These meetings – the first in more than three years, because of high tensions – are a vivid reminder that despite 60 years of animosity, misunderstanding, threats and occasional artillery exchanges, the world's most heavily armed border divides a single people.

The reunion came too late for 90-year-old Seo Jeong-suk, who died in South Korea just 15 days ago. Her daughter Kim Yong-ja, 68, sobbed as she handed her long-lost sister a framed photograph of Seo. Kim Yong-sil clasped the photo to her heart and said: "It's mum's photo."

For some other families, ageing and illness did not thwart the reunions but made them bittersweet.

"Sister, why can't you hear me?" North Korean Ri Jong-sil, 84, asked 87-year-old Lee Young-sil, who has difficulty recognising people because of Alzheimer's disease.

Ri cried as Lee's daughter, in tears, told her mother: "Mum, it's my aunt. It's my aunt. She's your sister."

The sisters' different family names are a product of the Korean peninsula's division: it's the same family name, but each country uses different spelling rules in both Korean and English.

South Korean Kim Sung-yoon, right, is reunited with her North Korean sister. Photograph: Pool/Getty Images

Ri Chol-ho, 77, from North Korea, used a piece of paper to communicate with his 81-year-old brother from South Korea, Lee Myeong-ho, who has a hearing problem.

"Mother used to tell me that you would return home and buy me a pair of rubber shoes," Ri wrote on the paper.

These Korean people are the lucky few. Millions have been separated from loved ones by the tumult and bloodshed of the three-year war that ended in 1953. During a previous period of inter-Korean rapprochement, about 22,000 Koreans had brief reunions – 18,000 in person and the others by video. None got a second chance to reunite, Seoul says.

The reunions were arranged recently after impoverished North Korea began calling for better ties with South Korea. Analysts from outside the Koreas say it is an attempt to win badly needed foreign investment and aid.

The North sent mixed signals by threatening to scrap the reunions in protest against annual military drills between Seoul and Washington, set to start on Monday.

Many in Seoul are also wary after last year's springtime threats from Pyongyang of nuclear strikes against Seoul and Washington. In recent years North Korea has conducted nuclear and missile tests, and is blamed for attacks in 2010 that killed 50 South Koreans.

Last week, North Korea decided to honour its earlier promise to allow the reunions after South Korea agreed to Pyongyang's proposal that the rivals stop insulting each other. In South Korea, there are still worries that the reunions might be disrupted because of the impending military drills.

Lee Son-hyang of South Korea, left, with North Korean relative Lee Yoon-geun. Photograph: Yonhap/AFP/Getty Images

The reunions are broken into two parts. Thursday's reunions end on Saturday, and a second group of about 360 South Koreans is expected to visit the mountain resort on Sunday to meet 88 elderly North Koreans. Those reunions will end on Tuesday.

Both governments ban their citizens from visiting each other or even exchanging letters, phonecalls and emails.

In Pyongyang many people had heard about the plan to hold the reunions on the television news or other state media. "I desperately hope for reunification. We are of the same blood, and getting these families together will help national reunification," said 63-year old Jang Hye-sun.

The two Koreas have been in a near-constant standoff since an armistice ended the Korean war. It hasn't been replaced with a peace treaty, leaving the peninsula still technically in a state of war, and about 28,000 US troops are stationed in South Korea to help deter aggression from North Korea.

In 2000, South Korea created a computerised lottery system for people hoping for reunions, and since then nearly 130,000 people, most in their 70s or older, have entered. Only about 70,000 are still alive.

It's not known how North Korea selects people to attend reunions. It was only through the application process that 93-year-old Kang Neung-hwan even realised that he had left a son behind when he left North Korea during the war. Kang Jong-kuk, now 64, had been in his mother's womb at the time, and his father had not been aware that she was pregnant.

When they finally met on Thursday, the elder Kang could not resist a little gentle teasing.

"You look old," he told his son. "Come give me a hug."