In joining the international community's outrage UNHCR has urged Bangladesh to undertake an immediate investigation into the killing of Rohingya leader Mohib Ullah and hold those responsible to account.

"UNHCR is deeply shocked and saddened by the tragic killing of Rohingya leader Mohib Ullah in Cox's Bazar. We condemn this attack in the strongest possible terms," said the UN Refugee Agency.

The UNHCR extended deepest condolences to Mohib Ullah's family, and to the wider Rohingya community who are mourning his loss.

UNHCR said they are in contact with law enforcement agencies and governmental authorities in charge of maintaining safety and security for the Rohingyas living in the camps.

The agency has enhanced its staff presence in the camps to ensure that the Rohingyas have direct access to support services and can report their concerns.

"Protection and assistance services, including psychosocial support, are being provided to respond to the specific needs of individuals. Trained professionals and refugee volunteers are responding to helplines for refugees," said the UNHCR.

The Rohingyas fled to Bangladesh seeking safety and security from violence in Myanmar. "We continue to work together with authorities and partners to ensure the safety, wellbeing and protection of Rohingya refugees."

UN Resident Coordinator in Bangladesh Mia Seppo said his killing is a painful reminder of increasing risks of violence faced by activists promoting peaceful solutions to violent conflict.

"We pay tribute to Mohib Ullah, a voice of the Rohingya refugees, disenfranchised of their rights in Myanmar, living with uncertainty and insecurity," she tweeted.

The Embassy of the European Union (EU) also tweeted to say that the "murder" of the Rohingya leader and human rights activist "is a tragic event".US Ambassador Earl R Miller and British High Commissioner to Bangladesh Robert Chatterton Dickson have expressed deep shock at the alleged murder of leading Rohingya community leader Mohib Ullah.

"We extend our condolences to his family. We hope that the authorities succeed in bringing to justice those who committed his killing," the Embassy said.

Mohib Ullah, 46, chair of the Arakan Rohingya Society for Peace and Human Rights (ARSPH), was shot and killed by unidentified gunmen in Kutupalong camp in Cox's Bazar on Wednesday night.

"Saddened and disturbed by the murder of Mohammad Mohib Ullah, a courageous champion of the human rights of the Rohingya community," Miller tweeted.

He offered his condolences to Mohib's family and hoped that the perpetrators of the crime are brought to justice.

High Commissioner Dickson said that he was shocked and saddened by the murder of Mohib, the leader of the Arakan Rohingya Society for Peace and Human Rights.

"A tragic loss to his family, friends and the Rohingya community. My sincerest condolences," he tweeted.

The Human Rights Watch (HRW) has sought urgent investigations into Mohib Ullah's killing along with other attacks on Rohingya activists in the camps.

"Mohib Ullah was a vital voice for the community of Rohingya who had suffered unimaginable loss and pain when they arrived as refugees in Bangladesh," said Meenakshi Ganguly, South Asia director at Human Rights Watch on Thursday.

"He always defended the rights of the Rohingya to safe and dignified returns and to have a say in the decisions concerning their lives and future."

Mohib Ullah's death undermines not only the struggle of Rohingya refugees for greater rights and protection in the refugee camps, but also their efforts to safely return to their homes in Myanmar, Ganguly said.

Mohib Ullah had served as a leader among the nearly one million Rohingya refugees in Bangladesh, documenting the Myanmar military's crimes against the Rohingya and advocating for the refugees' rights in international forums.

The Amnesty International has called for a speedy investigation into the assassination of Mohib Ullah to bring the culprits to justice in fair trials.

In a statement received here on Thursday Saad Hammadi, Amnesty International's South Asia Campaigner, said the leading Rohingya activist's killing sent a "chilling effect" across the entire community.

"We call on the Bangladeshi authorities and the UN Refugee Agency to work together to ensure the protection of people in the camps, including refugees, civil society activists and humanitarian workers from both the Rohingya and host community, many of whom have shared concerns about their safety," said Hammadi.

Violence in the refugee camps in Cox's Bazaar has been a growing problem, he observed.

He said "Armed groups operating drug cartels have killed people and held hostages. The authorities must take immediate action to prevent further bloodshed."

Mohib Ullah had represented the Rohingya community at the United Nations Human Rights Council in 2019.

Mohib Ullah was a leading representative of the Rohingya community, who spoke out against violence in the camps and in support of the human rights and protection of refugees, said AI.

He also had campaigned for a safe and sustainable repatriation of more than 12 lakh Rohimgyas who fled to Bangladesh in 2017 to escape killings, rape and arson by Myanmar military regime.

Meanwhile, Fortify Rights has sought investigation into the murder of Rohingya human rights leader Mohib Ullah.

"This is a devastating loss for everyone who knew and loved Mohib Ullah, and it is also a tremendous loss for Myanmar, the Rohingya people, and the human rights movement more broadly," said Matthew Smith, Chief Executive Officer at Fortify Rights in a statement issued from Washington on Wednesday night.

He was committed to truth, justice, and human rights and the government of Bangladesh must immediately investigate anyone who may have been involved in this heinous crime and ensure justice, Smith said.

Mohib Ullah is believed to have been in his late 40s. He was the chairperson of the camp-based human rights organization ARSPH. He is survived by his wife and children.

Fortify Rights spoke with one eyewitness to the murder and four Rohingya refugees familiar with the situation, including two members of ARSPH. Fortify Rights also reviewed photographs and videos of the crime scene, said the statement.

Slain Rohingya leader Mohib Ullah was buried in Lambashia camp-1 in Kutupalong refugee camp in Ukhiya upazila on September 30.

Mohib Ullah's namaz-e-janaza was held at Lambashia mosque attended by a large number of Rohingyas from refugee camps Ukhiya and Teknaf upazilas, said his brother Habib Ullah.

Unknown gunmen sprayed 46-year-old Mohib with bullets on Wednesday (September 29) night.

Mohib Ulah was first rushed to a local medical facility and later referred to Cox's Bazar Sadar Hospital where the on-duty doctor declared him dead.