"Oman's security forces routinely harass, detain, and imprison rights defenders, social media users, and others critical of governmental policies," HRW said in a statement on its website.
"Oman should immediately release everyone detained solely for exercising their rights to freedom of expression, association, and peaceful assembly," the organization added.
Since pro-reform demonstrations in 2011 and 2012 in Oman, the county's authorities have repeatedly violated international human rights standards, according to the organization. During the demonstrations security forces convicted hundreds of protesters, relying on laws criminalizing "illegal gatherings" and "insulting" Sultan Qaboos bin Said Al Said.
Although the country's leader has released most of demonstrators detained in 2011 and 2012, Omani security forces "continue to harass and detain peaceful activists, relying on overly broad laws that criminalize the peaceful exercise of basic rights", said the organization.
"Oman should stop arresting its critics and join all relevant international rights treaties as a first step to signaling its commitment to real reform," HRW's deputy Middle East and North Africa director Joe Storm was quoted as saying in the statement.
On September 13, the United Nations Special Rapporteur on the rights to freedom of peaceful assembly and of association Maina Kiai also criticized Oman for violating freedom of expression.
On September 25, HRW sent an open letter to the Omani authorities demanding information regarding the recent detentions of human rights activists and dissidents, but not yet received a response.