(New York) - The Syrian government, pro-government militias, and non-state armed groups should immediately release everyone they have arbitrarily arrested, abducted, and detained in the last three years for their peaceful, journalistic, and humanitarian activities. There have been new arbitrary detentions and abductions in Syria despite the United Nations Security Council's resolution on February 22, 2014, demanding an end to those practices and the release of everyone who has been arbitrarily detained. To emphasize the plight of those detained, a group of human rights groups, including Human Rights Watch, jointly initiated a campaign - http://free-syrian-voices.org/ - on the third anniversary of Syria's uprising on March 15 to highlight the cases of 37 Syrians jailed or abducted for their work. "After almost three years, the Security Council finally adopted a resolution demanding the release of detainees, but that has brought no relief to the many detainees in Syria's dungeons," said Nadim Houry, deputy Middle East director at Human Rights Watch. "Both the government and armed groups need to stop throwing people in detention and free everyone they are arbitrarily holding." The Violations Documentation Center, a Syrian monitoring group, reported that 13 people have been detained since February 22, and that 37,245 people are in detention by its count. On February 25 government forces arrested Firas Shehabi, who works for UNICEF, and his wife at their home in front of their 4-year-old daughter, a friend told Human Rights Watch. They remain in detention. Since the Syrian uprising began in March 2011, the government has arbitrarily detained, disappeared, and tortured peaceful political activists, journalists, humanitarian workers, doctors, and lawyers. The exact number held by the government is impossible to determine because the overwhelming majority of detention facilities are off limits to outsiders and those detained at security service sites are held incommunicado. Many in government facilities are held solely for exercising their rights to free expression and peaceful assembly, or for helping others exercise those rights, Human Rights Watch said. Members of Syria's multiple security agencies interrogate the detainees and often hold them for months without charge, in many cases torturing and otherwise mistreating them, and denying them communication with their families or with a lawyer. Security forces hold some in central prisons in big cities, but others are held in army barracks or detention facilities in branches of Syria's security services. While the majority of detainees are men, security forces have also detained women and children. The government often accuses political detainees of supporting "terrorism." Syria's government adopted a counterterrorism law in July 2012 that is broad enough to encompass almost any opposition activity. The law defines terrorism not just as violent acts, but as any act that can "destabilize public security," using "any method." Some detainees eventually appear in court, and others before military tribunals, but the fate of many others remains unknown. Armed groups opposed to the government have also arbitrarily detained people, including journalists, and in some cases aid workers and activists who have criticized the groups. The armed groups have also kidnapped and held civilians hostage to extract money from their relatives or to exchange them for detainees in government detention facilities. Taking hostages is a war crime under the statute of the International Criminal Court. If hostage taking is systematic or widespread, it can amount to crimes against humanity. People who had been detained by some of these groups have also told Human Rights Watch that they and others in custody were subjected to ill-treatment and torture. Groups, including the Islamic State of Iraq and Sham (ISIS), Jabhat al-Nusra, Suquor al-Izz, and the al-Farouq battalionhave also unlawfully executed detainees in their custody. In December 2013, unidentified men kidnapped a group of four human rights activists, including a prominent rights defender, Razan Zeitouneh, at their office in Douma, in the area of eastern Ghouta,an area in the suburbs of Damascus under the control of a number of armed opposition groups.Zeitouneh and her colleagues - Wael Hamada, Samira Khalil and Nazem Hammadi - are still missing. The armed groups have also kidnapped several humanitarian aid workers. On January 3, 2014, Médecins Sans Frontières (MSF) announced that an unknown rebel group had abducted five staff members in northern Syria. On October 13, 2013, unidentified gunmen kidnapped six International Committee of the Red Cross (ICRC) aid workers and one Syrian Arab Red Crescent volunteer in Saraqib, Idlib.Workers from MSF and the ICRC as well as other humanitarian aid workers are still missing. Over 200 civilians, the vast majority women and children, were kidnapped on August 4, 2013, when an alliance of non-state armed groups took control of Alawite villages in Latakia countryside. According to an opposition military leader from Latakia working on subsequent hostage negotiations, as of early September ISIS was holding 110 to 120 of the abductees, and Jaish al Muhajiren wal-Ansar was holding 105. Later in September, control over the hostages held by both groups was transferred to another group, Ahrar al-Sham, according to the military leader. On March 12, 2014, in a news broadcast, Al-Jazeera Arabic released new images of some of these hostages and reported that the group holding them would release them in exchange for prisoners held by the Syrian government. The broadcast came in the wake of a prisoner exchange on March 9 between the government and the armed group Jabhat al-Nusra. The group exchanged 13 nuns it had been holding hostage for nearly four months for women and children that the Syrian government was detaining. The armed group had kept the abducted nuns in a house in the town of Yabroud, outside Damascus, close to an area of recent military operations. Armed groups that have kidnapped and arbitrarily detained people should stop those practices, immediately free anyone in their custody, and treat all detainees in conformity with international human rights and humanitarian law standards, Human Rights Watch said. Governments and individuals that finance these groups should use their leverage to pressure the groups to release their hostages. All governments, companies, and individuals should also immediately stop selling or supplying weapons, ammunition, material, and funds to non-state armed groups committing kidnappings in a widespread or systematic way, until they stop committing these crimes and those responsible are fully and appropriately held to account. Arms sales and military assistance to these groups may make the individuals supplying them complicit in the crimes. UN Security Council Resolution 2139 strongly condemns the arbitrary detention and torture of civilians in Syria, as well as the kidnappings, abductions, and forced disappearances. The resolution demandsthe immediate end of these practices and the release of all arbitrarily detained people, starting with women and children, as well as sick, wounded, and elderly people, and including UN personnel and journalists. "Thousands of people are languishing in detention in Syria while parties to the conflict use them as bargaining chips," Houry said. "The Security Council should follow up on its recent resolution by demanding access to all detention facilities for independent monitors and referring the situation in Syria to the International Criminal Court. The parties need to understand that there will be consequences for these continuing abuses."