By William Horsley BBC News

Former sex slaves are still demanding official compensation

In their midst, a small group of elderly women sit silently.

They are the survivors of the brutal, Asia-wide system of sex slaves for the Imperial Japanese Army, which the military government encouraged and helped to operate for 13 years, from 1932 until the end of World War II in 1945.

They were euphemistically called "comfort women". But experts like Korean American scholar Edward Chang of the University of California say the network of "comfort stations" were actually officially-sanctioned rape camps.

Many of the women were even killed as part of an attempt to cover up the crime.

"There should be no time limit on prosecuting these crimes against humanity," Prof Chang said.

Japan says all potential claims by individuals for sufferings inflicted in the war were closed years ago, by treaties normalising its ties with other Asian countries.

But Kang Kyung-wha, a senior official at South Korea's foreign ministry, has recently urged Japan to come to terms with its "legal responsibility" and human rights obligations towards the former comfort women.

Repeatedly abused

Kim Gunja, now aged 80, is too frail to attend the Wednesday demonstrations.

Her story is typical of the tens of thousands - some estimates say 200,000 - women from across Asia whose lives were ruined when they became military sex slaves to the Japanese.

At the age of 17, she was tricked into being abducted by a Korean middle-man who delivered large numbers of young women and girls to his country's then Japanese colonial masters.

Kim Gunja is especially angry at current Japanese leaders

She was taken by train to the so-called comfort stations for the Japanese army in Manchuria, north-east China, where she says she was raped by the soldiers many times a day for three years.

"The soldiers didn't know when they would die, and they were very cruel," she said.

She was beaten so badly that she lost her hearing in one ear. After the war she could never marry or get a good job.

She still cannot forgive. And she saves her fiercest hatred for current Japanese leaders.

She wants them to show sincere atonement for Japan's past wrongdoings and to take responsibility by paying official compensation.

Facing up to the past

Japan stands accused of a series of evasions in facing up to the military sex slave issue.

According to Mr Chang, Japan's first admission of involvement only came in 1991, after a wartime document came to light in the foreign ministry about the granting of travel permits for Asian women in areas occupied by the Japanese army.

He says that, since then, the Japanese authorities have continued to hinder the search for detailed evidence about the fate of the former comfort women.

But his own research team's trawl through America's national archives has produced a sheaf of files captured by the US army from the retreating Japanese forces.

They contain photos and other personal details of dozens of young Filipino women - evidence, he says, of the most extensive system of female trafficking the world has ever seen.

Since 1992 Japanese prime ministers have all made formal apologies for the war.

But Shin Heisoo, head of the Korean council supporting the former military sexual slaves, believes these statements are just empty words.

Only legal reparations, she says, will suffice to acknowledge what she sees as war crimes.

In Japan, a recent opinion poll showed that only 13% of the population think further apologies to Asian countries are needed.

Many in South Korea cannot just forget the past

It also directly funded medical care for the recipients.

A director of the fund, Yasuaki Onuma, acknowledges the criticism of Japan's slow and limited response.

But he also holds some hard-line South Korean campaigners responsible for the impasse.

Many of the Korean victims, he says, were put under intense social pressures to refuse the Japanese donations, although they sorely needed that support.

It was recently decided that the fund will shut down within two years.

So the poison from past cruelties will be passed on to a new generation of Koreans and Japanese.

Kim Gunja now lives near Seoul in a home for former comfort women supported by the South Korean government. She says she hopes Japan will reveal the truth and offer her official compensation.