The U.N. says Secretary-General Antonio Guterres raised the plight of an estimated 1 million Uighurs incarcerated in re-education camps in China during a recent meeting with the country's president, Xi Jinping.

U.N. spokesman Stephane Dujarric told reporters Monday the U.N. chief told the Chinese leader that "human rights must be fully respected in the fight against terrorism and in the prevention of violent extremism."

Criticism has grown over China's internment of Uighurs as well as members of other predominantly Muslim ethnic groups. Last week, Human Rights Watch executive director Kenneth Roth wrote a harsh op-ed accusing Guterres of being silent on human rights and failing to speak out publicly on the plight of the Uighurs.

Dujarric called Guterres' discussions with Xi "very cordial" and "frank."