South Korea has announced it has arrested a two-star general on charges of leaking the country's entire war plan to North Korea.

It is the latest in a series of arrests of alleged North Korean spies, including a woman accused of using sex to secure sensitive information.

The alleged spy is accused of giving Pyongyang South Korea's entire war plan, which includes preparations and responses to be implemented in the event of a conflict with the communist North.

The general was allegedly paid for betraying his country when the plans were passed on to a North Korean agent in China.

The leak is the latest in a series of damaging blows to South Korea's security.

Two alleged North Korean assassins are about to go on trial in the South charged with attempting to kill a senior North Korean defector.

The former head of the North Korean workers party and tutor to Kim Jong-il, Hwang Jang Yop, defected to the South in 1997.

The two assassins apparently trained for six years to carry out the assassination mission.

They came to the South posing as defectors, but were caught as they were preparing to strike.

And in another case, a North Korean woman allegedly posing as a defector has been arrested for passing on plans of Seoul's subway system to Pyongyang.

She is accused of sleeping with a subway official to obtain the plans, which are now in the hands of Kim Jong-il's regime.

One of South Korea's chief spy hunters, prosecutor Oh Se-in, says the North is intensifying its spy missions into the South while their focus has been on the sinking of a South Korean warship in March.

He says it is a two pronged war - the visible war involving guns, ships and soldiers, and then the clandestine war involving spies, sex and secret plans.

However, despite recent tensions the South has approved two shipments of humanitarian aid to the North.

South Korea's Unification Ministry says it has approved two private shipments of baby formula.

The aid is worth hundreds of thousands of dollars and will be sent this month.

Impoverished North Korea is suffering severe food shortages, and the United Nations estimates that one in three of its children is stunted by malnutrition.

Seoul says it will continue to offer humanitarian aid to Pyongyang, despite the recent tension.