The picture taken on February 7 shows Panmunjom, also called the Joint Security Area, in the DMZ that divides the two Koreas. Photo:VCG

North and South Korea signaled a surprise thaw in relations on Tuesday, announcing the restoration of cross-border communications that were severed more than a year ago and an agreement between their two leaders to improve ties.

The joint announcement, which coincided with the anniversary of the end of the Korean War, was the first positive development since a series of summits between the North's leader Kim Jong-un and the South's President Moon Jae-in in 2018 failed to achieve any significant breakthrough.

The two sides revealed that Kim and Moon had exchanged a series of letters since April in which they agreed that reestablishing hotlines would be a productive first step in rebooting relations between the two countries who, despite the end of their 1950-53 conflict, remain technically at war.

"The top leaders of the North and the South agreed to make a big stride in recovering the mutual trust and promoting reconciliation by restoring the cutoff inter-Korean communication liaison lines," North Korea's official KCNA news agency reported.

Pyongyang cut off all official military and political communication links in June 2020 over South Korean activists sending anti-Pyongyang leaflets across the border until the two sides said all lines were restored on Tuesday.

They exchanged their first phone call since the suspension on Tuesday morning, Seoul's unification ministry said, with the defense ministry adding that military hotlines were also back to normal operation.

Moon's office said that ­restoring the hotlines was the first step toward improving ties.

"The two leaders also agreed to restore mutual trust between the two Koreas as soon as possible and move forward with the relationship again," it added in a statement.

Moon is credited with brokering the first-ever summit between North Korea and a sitting US president in Singapore in 2018. But Pyongyang cut off contact with Seoul following the collapse of a second summit between Kim and then US president Donald Trump in Hanoi that left nuclear talks at a standstill.

After US President Joe Biden took office, Kim said in June that Pyongyang needed to prepare for both "dialogue and confrontation" with Washington - but with a particular emphasis on the latter.