ISTANBUL—Three Uyghurs who fled from China to Turkey have described forced abortions and torture by Chinese authorities in China’s far western Xinjiang region, ahead of giving testimony to a people’s tribunal in London that is investigating if Beijing’s actions toward ethnic Uyghurs amount to genocide. The three witnesses include a woman who said she was forced into an abortion at six and one-half months gestation, a former doctor who spoke of draconian birth control policies, and a former detainee who alleged he was “tortured day and night” by Chinese soldiers while he was imprisoned in the remote border region. They spoke to The Associated Press of their experiences before testifying by video link to the independent U.K. tribunal, which is expected to draw dozens of witnesses when it opens four days of hearings on June 4. The tribunal, which does not have U.K. government backing, will be chaired by prominent …