The life of hunger striker Alaa Abd el-Fattah is in grave danger, according to the United Nations High Commissioner for Human Rights Volker Turk, who renewed his call for Egypt to release him immediately.

Abd el-Fattah, a prominent activist and blogger, was sentenced to five years in prison in December 2021 for spreading false news and has been on a hunger strike for 220 days in protest of his detention and prison conditions.

He informed his family that he would stop drinking water on Sunday in an escalation of his protest. His mother says she did not receive the usual letter from him when she visited on Monday.

He “is in great danger. His dry hunger strike puts his life at acute risk,” Turk said in a statement.

Without water, Abd el-Fattah’s health could rapidly deteriorate. The escalation of his protest coincides with the COP27 climate summit, the United Nation’s annual gathering of world leaders to discuss global warming being held this year in Egypt.

Ravina Shamdasani, the spokesperson for the U.N. top human rights official, said Turk had personally spoken with Egyptian authorities to appeal for Abd el-Fattah’s release, most recently on Friday.

Asked whether there was a risk he may have already died, given the lack of communication, Shamdasani told a briefing in Geneva: “We are very concerned for his health and there is a lack of transparency as well around his current condition.”

Abd el-Fattah’s detention has become a prominent issue at the COP27 summit in Sharm el-Sheikh, which his sister is attending to campaign for his release.

Asked about the case, Egyptian Foreign Minister and COP27 President Sameh Shoukry told CNBC that prison authorities would provide Abd el-Fattah with healthcare. Egyptian officials have not responded to Reuters phone calls for comment on Abd el-Fattah. They said previously that he was receiving meals.