GENEVA - Life in Syria is becoming exemplified by escalating abductions and enforced disappearances, U.N. High Commissioner for Human Rights Navi Pillay has warned, expressing concern at the callous indifference to human life in the war-ravaged country.

"In just the past few months, we have seen a significant and deeply alarming rise in abductions of human rights defenders, activists, journalists, religious figures and others by armed opposition groups, as well as the continuing arbitrary detention and enforced disappearances of individuals by Government forces in Syria," Pillay said in a statement Friday.

The High Commissioner also expressed concern over the apparent abduction of 12 nuns from Maaloula and called for their immediate and unconditional release.

Bishop Selwanos Boutros Alnemeh of Homs and Hama has repeated an appeal for the release of 12 women religious kidnapped in Syria on December 2.

The nuns are Sisters from the Convent of St Tekla in Maalaoula, a largely Christian town north of Damascus. Pope Francis had last weekend appealed for their freedom.

Syrian Orthodox Bishop Alnemeh said in an interview with the Catholic charity Aid to the Church in Need that he had not heard from the sisters since their disappearance 10 days ago, the think-tank Ekklesia reported.

He said he believes that the women are now being held in Yabrud, which is 12 miles (20 kilometers) from Maaloula.

"I demand the immediate release of the nuns, who have done no harm to anyone. We've reached the point where even nuns are being abducted. What have they done wrong? It's a crime. The abductors want to demonstrate that they know no mercy.

"[The Sisters] were neither on the side of the regime nor on that of the opposition. In the convent they took in war refugees without regard for their religion including Muslims," said Bishop Alnemeh.

In her statement, Pillay gave details of other abudctions.

On December 9, five masked gunmen reportedly stormed into a joint office for two human rights and humanitarian NGOs, the Violations Documentation Center, and the Local Development and Small Projects in opposition-controlled Douma in Rif Dimashq.

They abducted award-winning Syrian human rights defender Razan Zaitouneh. Her husband, Wa'el Hamada, who is a prominent activist and former political prisoner, and two other colleagues, Nazem Hamadi and Samira Khalil, were also abducted.

"Human rights defenders, humanitarian aid workers and activists take great personal risks on a daily basis to document human rights violations throughout Syria, and provide much-needed humanitarian aid to people, including those under siege," Pillay said.

"I urge all parties to the Syrian conflict to stop terrorising civilians through abduction, hostage-taking, enforced disappearances and arbitrary detention, in clear violation of international human rights and humanitarian law.

"I call on all parties to the conflict to refrain from targeting civilians and to immediately release all those who are deprived of their liberty in violation of international law." Pillay stressed.

The abductions of Zaitouneh and her colleagues came just hours after the families of two Spanish journalists, who were abducted in Syria nearly three months ago, appealed publicly for their release.

They are among dozens of other journalists who have been abducted in the course of the conflict in Syria. Major news organisations have warned that the increasing risk of abduction will deter reporting from inside Syria.

"The government and armed groups have the obligation under international law to take all necessary steps to ensure that all civilians, including human rights defenders, are protected from any intimidation or violence as a result of their activities," Pillay stressed.

"Under international humanitarian law, attacks against journalists are strictly prohibited. Their work is indispensable in times of conflict and must be protected."

Vatican Radio carried a report on the concerns of major news organizations about the safety of journalists reporting in Syria.

It reported that 13 news outlets have sent a letter to the leadership of the armed opposition in Syria, calling for urgent action against rebel groups increasingly targeting journalists for kidnappings.

The letter is in response to a sharp rise in the number of journalists while on assignment in opposition-held areas in northern Syria.

Many of the abduction cases go unreported at the request of families or employers in the hope that keeping the kidnappings out of public view may help with negotiating the captives' release.

It is believed that up to 40 Syrian and foreign journalists are being held against their will and the lack of response to individual mediation efforts have encouraged some families and employers to speak out.

Soazig Dollet, head of the Middle East and Africa Department for Reporters Without Borders said, "since early September we can really notice an increased number of kidnappings not only on foreign journalists but also of Syrian news providers."

Melkite Greek Catholic Gregorios III of Antioch also appealed for the release of the Syrian nuns. He said that they should be returned without delay to the care of Greek Orthodox Patriarch John X of Antioch.

Both Patriarch Gregorios and Bishop Alnemeh said that they have no news of the whereabouts of Patriarch John X's brother, Archbishop Paul Yazigi and Archbishop John Ibrahim, who were both abducted in April 2013 while returning to Aleppo.