Stefan Rousseau, Associated Press
Foreign Secretary William Hague and actress Angelina Jolie arrive at the 'End Sexual Violence in Conflict' summit in London, Tuesday, June 10, 2014. They are hosting a four-day summit on sexual violence in war zones, attended by officials from over 100 countries. The summit, starting Tuesday, aims to identify ways to improve investigation of sexual violence and provide support for women and girls.

LONDON — Angelina Jolie appealed for a change in attitude on a topic she said has been taboo for too long, bringing the power of her celebrity Tuesday to an international summit to stop sexual violence in conflict zones.

Opening the four-day London summit, the Hollywood star spoke with passion and conviction, recalling her meetings with rape victims who struggle with injustice and stigma long after their countries have emerged from conflict.

"We must send a message around the world that there is no disgrace in being a survivor of sexual violence, that the shame is on the aggressor," she said, to cheers from the audience. "We need to shatter that culture of impunity."

Jolie and British Foreign Secretary William Hague are co-hosting the event, billed as the largest such gathering on the subject ever. Diplomats, officials and non-profit representatives from more than 100 countries gathered to press for the rights of victims — both women and men alike.

Echoing Jolie's words, Hague called sexual violence "a moral issue for our generation."

"As was said with slavery in the 18th century, now we know the facts, we cannot turn aside," he said.

Others far afield also offered support. Pope Francis, who has made combatting sex trafficking and human slavery one of his priorities, sent a tweet Tuesday to encourage the summit's outcome, saying "Let us pray for all victims of sexual violence in conflict, and those working to end this crime."

Hague and Jolie are set to launch a guidance document on best practices Wednesday to help strengthen prosecutions for rape in conflicts. The document also aims to help train soldiers and peacekeepers to deal with the issue.

The pair have campaigned hard on the issue for two years, and on Tuesday they were welcomed with cheers from others fighting for the cause. The mood in London spoke of empowerment, with a lively fringe program featuring photo exhibitions, poetry readings, artists performing skits and hip hop music. A marketplace selling clothes and crafts made by rape victims in Somalia and Congo did brisk business.

Nigerian rap and soul singers sang about rape and other problems facing young Africans, while volunteers taught Swahili folk songs in workshops similar to those performed in conflict zones to help reduce trauma. An eclectic group of charity workers and computer experts brainstormed on ways to use technology to improve reporting on sexual violence.

With the cameras of the world focused on her, Jolie urged her audience to demand change. Having traveled to conflict zones from Afghanistan to Somalia as a U.N. envoy, she said she wanted others to share in what she had learned, and dedicated the conference to a rape victim she and Hague recently met in Bosnia.

"She felt that having had no justice for her particular crime, in her particular situation, and having seen the actual man who raped her on the streets free, she really felt abandoned by the world," Jolie said.

"This day is for her."