SEOUL - IMPOVERISHED North Korea has spent an estimated US$700 million (S$1 billion) this year on nuclear and missile tests, enough to solve its food shortage for at least two years, South Korean news reports said on Monday.

The figure includes the estimated US$43 million cost of test-firing five Scud and two Rodong missiles Saturday, according to unidentified government officials quoted by Chosun Ilbo newspaper.

The latest tests, staged on the US Independence Day holiday, were seen as a show of defiance to Washington as it seeks tough enforcement of UN sanctions aimed at shutting down the communist state's nuclear and missile programmes.

Officials quoted by Chosun estimated it cost US$300 million to launch a long-range Taepodong-2 missile on April 5, and another US$10 million to launch 10 short-range missiles in recent weeks.

In addition, they estimated the May 25 underground nuclear test - the country's second since 2006 - cost between US$300-400 million. JoongAng Ilbo gave similar figures. Neither paper gave the methodology for the cost calculation.

Chosun quoted an unidentified official as saying the North could have bought one million tons of rice on the international market for 300 million dollars.

The United Nations World Food Programme has said that according to a study last year, nearly nine million North Koreans - more than a third of the country's 24 million people - are estimated to need food aid.

Saturday's launches were the biggest salvo of ballistic weaponry since the North fired a Taepodong-2 and six smaller missiles in 2006, also on July 4 US time.

US Vice President Joseph Biden on Sunday dismissed the launches as 'like almost attention-seeking behaviour' and said the focus was on further isolating Pyongyang.

The chief nuclear negotiators from Japan and South Korea held talks in Seoul Monday on the North Korean nuclear issue and the weekend missile tests. -- AFP