North Korea on Wednesday proposed holding top-level military talks with South Korea but it was unclear what it wanted to discuss, Seoul's defence ministry said. "North Korea proposed general-level talks on May 8-10 at Panmunjom," a joint security area in the buffer zone dividing the two Koreas, a spokesman said.

Seoul on Monday had urged the North to hold working-level military talks this week at Panmunjom, to prepare for the first test runs of railways across their heavily fortified frontier in half a century.

The North's response was contained in a brief message sent in the name of a three-star general, Kim Yong-Chol, who is the North's chief delegate to the general-level talks. The last meeting of generals was held in 2006.

"It is not known yet what the North wants to talk about," the spokesman said.

Seoul is considering the invitation, which coincided with attacks by Pyongyang over what it called South Korea's military build-up.

Minju Joson, the government daily, said South Korean authorities were "getting frantic" in their moves to reinforce and develop ultra-modern war hardware.

"This is a very dangerous criminal act of blocking the process of peacefully settling the nuclear issue on the Korean Peninsula, escalating military tension and driving the situation to the phase of confrontation and war," it said.

"The North will never remain a passive onlooker to the US and South Korean warlike forces' reckless war moves against it behind the curtain of dialogue, but take measures to resolutely counter them," it said.

The North's state media has voiced similar attacks in the past on the US-South Korean military alliance.

The two Koreas have agreed to conduct test runs of cross-border railways on May 17 and to try to ensure there is a military guarantee for their safe operation.

A previous attempt to carry out the test runs failed last year because the North Korean military was reluctant to open the sensitive border area to commercial traffic.

The plan to connect the railways across one of the world's most dangerous flashpoints is a flagship project for relations between the two nations, which have remained technically at war since their 1950-53 conflict.