South Korea said Wednesday that it has taken delivery of Patriot missiles to protect against attack by North Korea and they would be operational within two years.

The delivery is part of Seoul's plan to build its own defence system against North Korea's major missile capability.

"We have set 2010 as a target year for deploying Patriot missiles for operational use," defence ministry spokesman Won Tae-Jae told a briefing.

"We are in the middle of taking them over."

He said the Patriots were being checked before deployment, but refused to reveal how many had been delivered or when or where they would be deployed.

South Korea previously announced plans to buy 48 second-hand PAC-2 Patriot missiles from Germany starting this year.

The United States, which bases 28,500 troops in South Korea, has upgraded its Patriot batteries there with advanced PAC-3 missiles to better protect its troops and bases.

It is developing US-based defences against long-range missiles.

The US and its allies regard the North's missile development as a major threat to regional security, on top of its nuclear ambitions.

North Korea has deployed two types of Scud missile with a range of 300-500 kilometres (187-312 miles) range as well as Rodongs, which have a range up to 1,300 kilometres.

It is developing longer-range Taepodong missiles that could theoretically reach the US state of Alaska.

Defence officials in Seoul believe the North has 300-500 Scuds or Rodongs.

The North alarmed the region by test-firing a Taepodong-1 in 1998 over Japan. It test-launched a Taepodong-2 in 2006 but it failed.

The communist state is building a new launch site for long-range missiles on its west coast and reportedly carried out an engine ignition test for the Taepodong-2 there this year.

General Walter Sharp, the US troop commander in South Korea, said in April the country was vulnerable to North Korean missile attacks and should develop a "systematic" missile defence system.

Despite being a longtime US ally, South Korea has not joined the United States and Japan in efforts to develop joint missile defences.