The United Nations on Monday voiced concern over the detention of 16-year-old Palestinian activist Ahed al-Tamimi.

"What is clear is that people need to have their rights respected. The detention of children is our particular concern and we have made those concerns known," U.N. spokesman Stephane Dujarric told reporters, according to Anadolu Agency.

Al-Tamimi is well known for her bold activism for a free Palestine. Videos and pictures of her confronting and slapping Israeli soldiers have been viral for weeks.

Earlier, the teenager and her mother Nariman were ordered to be detained behind bars for an additional eight days by Ofer Court, located near the West Bank city of Ramallah. The U.N. spokesman also expressed deep concern for the safety and protection of tens of thousands of people in southern Idlib and rural Hama in northeastern Syria.

"With the seventh winter of the conflict underway, more than 13 million people need basic aid and protection. While some parts of Syria are witnessing a welcome reprieve from hostilities, many others face intensified military operations and conflict," Dujarric added.

Dujarric said U.N. humanitarian chief Mark Lowcock is scheduled to visit Syria from January 9 to 12.

"He will assess the humanitarian response and discuss how to improve access and delivery with key interlocutors," he added.

On social media, Palestinians celebrated Ahed as a hero in widely distributed cartoons. In one, she is shown in a Joan of Arc-like pose, raising a Palestinian flag, framed by her easily recognizable mane of dirty blonde curls.

On Dec. 19, Israeli forces detained Ahed in Nabi Saleh. Her mother and cousin were arrested shortly afterward. The latest case is not Ahed's first brush with the Israeli authorities. In 2012, Istanbul's Basaksehir Municipality awarded her the Hanzala Courage Award for defying Israeli soldiers who had just arrested her brother. Then Turkish Prime Minister Recep Tayyip Erdogan met Ahed to personally convey his admiration. Ahed's father, mother and brothers have also all been repeatedly arrested by the authorities for their opposition to Israel's decades-long occupation.

The detention of Tamimi also highlighted the issue of arrests of Palestinian minors. Defense for Children International-Palestine, a local group, said 331 Palestinians under the age of 18 were held in military detention as of May, according to the most recent statistics released by Israeli authorities, as reported by The AP. It said that in 2016, an average of 375 minors were in detention each month. The Israeli military was unable to provide data on the number of minors it is holding.