Angelina Jolie joined British Foreign Secretary William Hague to visit Rwanda on Monday in a bid to encourage world powers to do more on tackling rape and sexual assault in war zones.
Britain's Foreign Office released a picture of the US film star and Hague getting off a British-flagged jet in the central African country.
They are also to visit the neighbouring Democratic Republic of Congo this week in a trip aimed at forcing the Group of Eight world powers to address the issue more seriously.
Hague said he would be making it his priority when he hosts the annual meeting of G8 foreign ministers next month in London.
"This visit is about hearing first hand from people who have endured rape and sexual violence during the conflict in the eastern DRC," Jolie said.
"We want to learn the lessons that their experience holds for how the world can protect thousands of women, men and children at risk of rape in many other conflict zones.
"And we want to persuade governments around the world to give this issue the attention it deserves.
"Unless the world acts, we will always be reacting to atrocities, treating survivors rather than preventing rape in the first place."
Jolie and Hague are calling on the G8 to agree that rape and sexual violence constitute breaches of the Geneva Conventions governing warfare.
They also want a new international protocol on the documentation and investigation of the issue.
Hague said: "More often than not the international community looks away, the perpetrators of these brutal crimes walk free and the cycle of injustice and conflict is repeated. We have to shatter this culture of impunity.
"It is time for real, meaningful action by the governments of the world to say that the use of rape as a weapon of war is unacceptable, to bring perpetrators to justice and to lift the stigma from survivors.
"This is my personal priority for the meeting of G8 foreign ministers."
The campaign will also be taken to the United Nations Security Council in June and the UN General Assembly in September.