The two Koreas spoke over a hotline for the first time after nearly two years in a diplomatic breakthrough ahead of proposed bilateral talks on the North's participation in the Winter Olympic Games.
After North Korea initiated the call yesterday at 3.30pm (2.30pm in Singapore), officials from both sides spent 20 minutes ironing out technical issues, South Korea's Unification Ministry said, without giving details.
Pyongyang had suspended the hotline, installed at the truce village on the inter-Korea border, in February 2016 in protest against Seoul closing down the joint Kaesong industrial complex.
North Korea's decision to reopen the communication channel was announced on state TV yesterday, after its leader Kim Jong Un abstained from making any provocations in his New Year's Day speech and instead proposed holding talks on sending the North's athletes to next month's Winter Games.
The breakthrough came after US President Donald Trump, in yet another war of words with Mr Kim, who warned the US on Monday that the nuclear button is "always on my desk", tweeted that he had a "much bigger and more powerful one than his, and my button works".
The US maintains that it has not changed its hardline stance against the North, and that it will continue to exert maximum pressure to isolate the nuclear-armed regime.
In Seoul, however, the mood was upbeat, with the presidential office and Pyeongchang, the city hosting the sporting event, welcoming North Korea's announcement.
The International Olympic Committee, which has the authority to allow selected North Korean athletes to compete, also said it will review North Korea's overture "in an open way".
Presidential press secretary Yoon Young Chan said it is significant to restore dialogue, and that it "sends a signal towards continuous communication". Pyeongchang officials, meanwhile, expressed readiness to host North Korea and even offered to send a cruise ship to ferry its delegation to the South.
The possibility of forming a joint Korean team has also been raised, but Mr Lee Kee Heung, president of the Korean Sport and Olympic Committee, was cited as saying yesterday that such talk is premature.
"We will leave all possibilities open," he said, according to the Yonhap news agency.
South Korea's pro-rapprochement President Moon Jae In has been pushing to improve relations with the North, in the hope that it could lead to dialogue with the US and the eventual resolution of North Korea's nuclear threat.
A North Korean official said on TV yesterday that Mr Kim "highly appreciated" Mr Moon's support of his peace offering, and added that the North will be sincere and honest in contacting the South.
The official said Mr Kim also stressed that improving ties "totally depends on the two Koreas".
South Korea's Unification Ministry on Tuesday proposed holding high-level talks on Jan 9, but the North has yet to respond.
Analysts expect the North Korean leader to follow through with his New Year's Day overture.
"He cannot afford to be cavalier with these suggestions amid the current climate of extreme tensions because he knows that in reneging (on his offer), we no longer can take him at his word," said Dr Graham Ong-Webb, research fellow at the S. Rajaratnam School of International Studies.