South Korea will seek to expand a no-fly zone along its land border with North Korea to cover their maritime boundaries and the Han River estuary, an official at Seoul's defense ministry said Thursday.

Seoul and Pyongyang have set up a no-fly zone along the Military Demarcation Line under the September inter-Korean military agreement. But they have not agreed on any air buffer zone over the Northern Limit Line, a de facto sea border, and the estuary.

The extension to the NLL would be in line with the Koreas' summit agreement in April to transform the areas surrounding the tense boundary into a "maritime peace zone." The NLL has been a flashpoint as Pyongyang has disputed its legitimacy.

"When discussing (with the North) zoning off the areas near the NLL in the East and West Seas as a no-fly zone, we will also discuss applying the no-fly zone to the Han River estuary," the official said on condition of anonymity.

In future consultations with the North, the two sides could have a dispute over setting a median line for the flight restrictions. For the Han River estuary and the NLL in the East Sea, they may be able to easily reach an agreement, but they could clash over the West Sea part, observers said.

In the past, Pyongyang argued that the NLL in the West Sea should be redrawn further south as it was set unilaterally by the US-led UN Command after the 1950-53 Korean War.

The related issues are expected to be discussed when the Koreas open a joint military committee tasked with enforcing their September military agreement aimed at reducing tensions, building trust and preventing accidental clashes.

Seoul has been pushing to launch the committee within this year. (Yonhap)