South Korea on Monday warned against raised expectations of a major breakthrough in relations with North Korea, saying Pyongyang had some way to go before sanctions could be eased.

South Korea on Monday warned against raised expectations of a major breakthrough in relations with North Korea, saying Pyongyang had some way to go before sanctions could be eased.

The two Koreas agreed to resume a high-level dialogue during a surprise and extremely rare visit to the South on Saturday by a top-ranking delegation from Pyongyang led by Hwang Pyong-So -- widely seen as the number two to paramount leader Kim Jong-Un.

The sudden visit followed months of military tensions and triggered hopes of a reboot for inter-Korean relations.

But South Korean President Park Geun-Hye and other senior officials, whilst welcoming the unexpected visit, stressed that it only marked a beginning.

"We should make efforts to ensure that the high-level contact will lead to regular dialogue, not just a one-time dialogue," said Park, who has been the subject of vicious personal attacks in the North Korean state media in recent months.

Pyongyang still needed to demonstrate its willingness to improve inter-Korean relations through "sincere actions," she added.

Park, who came to office in early 2013, has repeatedly said the door to dialogue with Pyongyang is open -- even a possible summit with Kim Jong-Un -- but insists the North must first take a tangible step towards abandoning its nuclear weapons program.

The high-level dialogue that the two sides agreed to resume by early November has been in limbo for seven months. The last round in February resulted in the North hosting a rare reunion of families separated by the 1950-53 Korean War.

The cash-strapped North has demanded that Seoul lift unilateral sanctions imposed after the sinking of the South Korean naval corvette Cheonan in 2010.

South Korea says the vessel was torpedoed by a North Korean submarine, but Pyongyang has always denied any involvement.

"Our government's basic position is that these measures can be lifted only after North Korea takes a responsible step that the South Korean people accept," Unification Ministry spokesman Lim Byeong-Cheol told reporters.

In the meantime, Seoul will place a top priority on arranging another family reunion program, he said, calling it "the most urgent and important issue".

On Sunday, Unification Minister Ryoo Kihl-Jae had also played down talk of a sudden rapprochement following Saturday's visit.

"It's not good to be overly optimistic about inter-Korean relations," the minister said.

The two Koreas have remained technically at war since the 1950-53 Korean conflict, which ended with a ceasefire rather than a peace treaty.