Two days after North Korea's nuclear test, South Korea has touted a cruise missile capable of hitting targets in the North "anywhere, at any time".

The defence ministry yesterday gave the media a video presentation of the recently deployed missile being fired from a warship and a submarine.

"With this missile, we could hit any facility, equipment or individual target in the North anywhere, at any time of our choosing," Major General Ryu Young-jeo told the briefing.

Defence ministry spokesman Kim Min-seok said the missile had the accuracy to target a particular window on a building.

It has "deadly destructive power" that could "restrain the enemy headquarters' activities" in wartime, Kim said.

The defence ministry also said it would speed up the deployment of a "kill chain" system capable of detecting and destroying North Korean missiles.

South Korea's military has been on a heightened state of alert since Pyongyang first threatened the nuclear test which was eventually conducted on Tuesday.

It was the North's third test, following previous detonations in 2006 and 2009, and seismic data suggested it was significantly more powerful.

South Korean warships and aircraft equipped with highly sensitive detection devices were deployed following the test to collect any traces of radioactive fallout.

Xenon gases released in the detonation could be analysed to determine what fissile material was used.

Experts are keen to confirm suspicions that the North may have switched from plutonium, used in 2006 and 2009, to a self-sustaining nuclear weapons programme using uranium.

The defence ministry said any forensic material would be sent to the Korea Institute of Nuclear Safety for analysis.

The day after the test, South Korea said it would accelerate development of longer-range missiles that could also cover the whole of North Korea.

In October last year, Seoul agreed with the US to almost triple the range of its missile systems, with Seoul arguing it needed an upgrade to counter the North's missiles.

• Australia's government has cancelled a planned visit by North Korean diplomats following the nuclear test. Officials from Pyongyang were due to visit Canberra this week to reopen its embassy, which North Korea closed in 2008 for financial reasons.

"We postponed the arrival of North Korean diplomats in Australia as a gesture following this detonation," Foreign Minister Bob Carr told a Senate hearing yesterday. But Australia still plans to allow North Korea to reestablish its embassy, he said.

Additional reporting by Associated Press