Another major aid group is warning Kenya not to close the world's largest refugee camp, saying the move is pressuring tens of thousands of Somali refugees to return to their deeply unstable country.

A new Refugees International report says Somali refugees in the Dadaab camp in Kenya say they feel under pressure to leave for Somalia, where attacks by Islamic extremist group al-Shabab continue and hunger is widespread.

The U.N. refugee agency "claims that it only supports voluntary returns, but none of the refugees whom we spoke with in Dadaab said they felt like they have much choice," said Mark Yarnell, who wrote the report after visiting Dadaab and Somalia. "It is a failure of the international refugee response system that other options are not available."

The report says Kenya should lift its Nov. 30 deadline to close the camp, which has existed for a quarter-century and holds more than 250,000 people. It sprawls in a dry, thorny region near the border with Somalia, where many born in the camp have never been.

On Monday, Kenya's High Court will hear a petition filed by the Kenya National Commission on Human Rights to challenge the government's plan to close the camp, Amnesty International said Friday.

Groups including Doctors Without Borders, Human Rights Watch and the Norwegian Refugee Council also have expressed alarm in recent weeks over Kenya's reported pressure on Somali refugees to leave. They say large parts of Somalia remain insecure and aid for returnees is limited.

Kenya has expressed concern that some Dadaab residents are used by the Somalia-based al-Shabab to launch attacks inside Kenya. Kenyan President Uhuru Kenyatta has said repatriations will be voluntary and humane.

The Refugees International report urges the U.N. refugee agency to give Dadaab residents "reliable information" about security conditions in Somalia.