South Korea's military said on Monday that it has detected signs of North Korea preparing to send more troops and weapons, including suicide drones, to Russia to support its war against Ukraine.

North Korea has already provided 240mm multiple rocket launchers and 170mm self-propelled howitzers, and was seen preparing to produce more suicide drones to be shipped to Russia after leader Kim Jong Un guided a test last month, according to Seoul's Joint Chiefs of Staff (JCS).

"Suicide drones are one of the tasks that Kim Jong Un has focused on," a JCS official said, adding that the North had expressed its intention to give them to Russia.

Such drones have been widely used in the Ukraine war, and Kim ordered a mass production of the aerial weapons and an update of military theory and education, citing intensifying global competition, state media reported.

Seoul, Washington and Kyiv have said there are around 12,000 North Korean troops in Russia. The JCS said at least 1,100 of them had been killed or wounded, in line with last week's briefing by South Korea's spy agency which reported some 100 deaths with another 1,000 wounded in the Kursk region.

Pyongyang's growing military ties with Moscow could pose greater threats to Seoul as it modernises its conventional forces, deemed inferior to the South's, and gains combat experience, the official said.

Along the heavily fortified Korean border, the North has dispatched up to 10,000 soldiers to turn the area into a wasteland and install barriers and barbed wire in recent weeks, though the numbers fell to several hundred over the weekend, the JCS said.

The JCS released photos that it said showed a group of North Korean troops testing the electrified wire fence using a goat.

There is also a possibility that the North will test-fire an intermediate-range hypersonic missile around year-end ahead of U.S. President-elect Donald Trump's inauguration, while sending more garbage balloons to the South, it added.

North Korea has launched thousands of balloons with bags of trash attached to them since late May, saying it was responding to balloons carrying propaganda leaflets flown by South Korean activists.

"With the backing of Russia, they'll likely try to stage various strategic provocations next year, such as launching intercontinental ballistic missiles and conducting a nuclear test to enhance its negotiating power with the US," the official said.