Tuesday's launch of the "Malligyong-1" was Pyongyang's third attempt at securing a military eye in the sky after two failures in May and August.

North Korean state media claimed within hours of the launch that leader Kim Jong Un was already reviewing images of US military bases in Guam.

Seoul's National Intelligence Service told lawmakers the launch had been a success but cautioned it was too early to say if the satellite was working as Pyongyang claimed, adding the North had been given "feedback" by Russia after Kim met Russian President Vladimir Putin in September.

"After the summit with Putin, the North provided Moscow with the blueprint and data relevant to the first and second satellite launches. Russia in turn analysed those data and provided the North with feedback," the agency told lawmakers, according to a briefing by MP Yoo Sang-bum.

While the North claims the satellite is already functioning, the NIS -- which collected and analysed debris from one of Pyongyang's failed launches, finding it had no military utility -- said it was unlikely.

"Given it usually takes three years for satellite development, the current claims do not guarantee the North's satellite capability -- unless Pyongyang actually makes public those Guam base photos it mentioned," Yoo said.

- Deal suspended -

After the launch, Seoul partially suspended a five-year-old military accord and deployed "surveillance and reconnaissance assets" to the border, in what defence chief Shin Won-sik said Thursday was an "essential measure" to defend against the nuclear-armed North's growing threats.

North Korea's defence ministry on Thursday called Seoul's moves "reckless" and said it would also suspend -- in full -- the deal, saying Pyongyang "will never be bound" by the agreement again and would immediately beef up its own border security.

The North would now "deploy more powerful armed forces and new-type military hardware in the region along the Military Demarcation Line," the ministry said in a statement carried by the official Korean Central News Agency.

The North also fired a ballistic missile early Thursday, Seoul's Joint Chiefs of Staff said, adding that the launch had not been successful.

The ballistic missile launch is a harbinger of things to come, said Yang Moo-jin, president of the University of North Korean Studies.

"In order to show that their suspension of the agreement does not amount to just empty words, it is expected that there will be a demonstration of force by violating the maritime border, deploying coastal artillery ... and launching various missiles," he said.

"As a result, there will be increased possibility of accidental armed clashes along the Military Demarcation Line and an increase in the possibility of these accidental armed conflicts escalating into war."

- Satellite in orbit -

North Korea's Kim personally oversaw the satellite launch, state media photographs showed, and later reviewed images of US military bases in Guam, purportedly sent by the country's new eye in the sky.

Pyongyang's defence ministry repeated Thursday that the satellite launch was part of its "right to self-defence" and dismissed the "extremely hysterical" response from the South in particular.

South Korea "must pay dearly for their irresponsible and grave political and military provocations that have pushed the present situation to an uncontrollable phase," the ministry continued.

KCNA has said the satellite will begin a formal reconnaissance mission on December 1.

Successfully putting a spy satellite into orbit would improve North Korea's intelligence-gathering capabilities, particularly over South Korea, and provide crucial data in any military conflict, experts say.

The launch also appears to kick off a space race on the peninsula, experts said, with Seoul planning to launch its first spy satellite via a SpaceX rocket later this month.