An exhibition focusing on wartime sexual violence against women in the Philippines has opened at a Tokyo museum and resource center on former "comfort women."

Around 30 panels are on display at the Women's Active Museum on War and Peace, known as WAM, to show through their testimonies how the Filipino women were sexually exploited by Japanese soldiers and their struggle to achieve justice since the end of World War II.

At the opening ceremony on Saturday, Felicidad Reyes, 82, who was repeatedly raped by Japanese soldiers in 1943 at the age of 14 at a garrison near her school, told some 50 attendants, "I can't forget it even after such a long time."

"The war imposed hardships on me, and I hold a grudge against the war," she said.

The issue of sex slavery in the Philippines came to light in 1992 "when Ms. Maria Rosa Luna Henson came forward in response to a call by a local women's group," according to Yumiko Saito, a WAM steering committee member. About 400 more women have followed Henson.

Henson was raped by three Japanese soldiers in 1942 when she was 14 and then was detained at a comfort station for nine months from April 1943 after joining an anti-Japan guerrilla group, according to her testimony made before her death in 1997 at 70.

She was reluctant at first to step forward, but her daughter encouraged her. "Although I suffered rough derision and insults, I felt my half-century of pains and burdens were gradually mitigated through activities (to seek justice)," she said in her testimony. A panel displaying her words is among the exhibits.

Another showpiece is a large quilt made by a victim of sexual slavery, who vividly depicts her wartime experiences, including scenes of sexual abuse by Japanese soldiers.

The exhibition also introduces local activities in support of the former comfort women. Saito said, "Supporters are now working to hand on the (stories of the) experiences of the victimized women to younger generations."

A coordinator of one of the groups was also invited to the opening ceremony. Rechilda Extremadura said it is a race against time to achieve full justice for the victims, given their advanced age.

Since its establishment as Japan's only resource center on wartime sex slavery in August 2005 -- the 60th anniversary of the end of World War II -- WAM has held exhibitions on wartime sex slavery in the Korean Peninsula, East Timor and China.

WAM director Eriko Ikeda said the decision to focus this time on the Philippines is because "recent research has led to the discovery of many historical documents on the issue."

It still remains unclear, however, how many women were exploited and how many comfort stations, or "rape stations," were established in the Philippines, she said.

"Japanese soldiers were deployed not only in major urban areas but also in mountainous areas. Studies are still going on about their involvement in sexual violence, particularly in the less populated areas," Ikeda said.

The exhibition, "The Philippines -- Struggling Lolas," runs until June 17, 2012. It is open every Wednesday to Sunday from 1 p.m. to 6 p.m., except national, year-end and New-Year holidays. "Lola" means grandmother in Tagalog.

For future projects, WAM, a private institution, intends to depict wartime sex slavery in Indonesia, Malaysia, Taiwan as well as Okinawa, where a number of comfort stations were built and where sexual abuse of local women has continued even after the end of the war because of the presence of U.S. military facilities, according to Ikeda.

Internationally, Japan has come under pressure to address the issue.

In 2007, the U.S. House of Representatives approved a resolution on comfort women demanding that Japan apologize for sexually enslaving them.

In 2008, the U.N. Human Rights Council urged Tokyo to "take immediate and effective legislative and administrative measures to adequately compensate all survivors as a matter of right."

Within Japan, around 35 municipalities nationwide have so far adopted statements to urge the state to make sincere efforts to respond to the victims, according to the WAM's website.