Human Rights Watch on Saturday urged European Union foreign policy chief Catherine Ashton to secure the release of Bahraini opposition activists ahead of an EU-Gulf Cooperation Council ministerial meeting in Manama.
The New York-based rights group called on Ashton in a statement to "pursue with Bahrain the immediate release of 13 high-profile activists and others detained or imprisoned for peacefully exercising their rights".
Currently 13 opposition leaders are serving prison terms for playing a role in an uprising in Bahrain in 2011 led by the Shiite opposition.
A court handed down life sentences to seven of the accused, including rights activist Abdel Hadi Khawaja, who also holds Danish nationality, and gave the others jail terms ranging from five to 15 years.
Lotte Leicht, EU director at Human Rights Watch, said it was vital for Ashton and EU member states to raise the issue at Sunday's meeting.
"If human rights are truly at the centre of the EU's foreign relations... then the high representative and member states need to show it at the EU-GCC meeting by vigorously pressing for the release of the Bahraini activists," she said.
Bahrain, a Gulf kingdom ruled by the Sunni Al-Khalifa dynasty, was shaken in February and March 2011 by demonstrations led by the Shiite majority.
The security forces crushed the month of protests, but demonstrations still take place regularly in Shiite villages around the capital.
Ashton is set to chair the joint EU-GCC meeting in Manama with Bahraini Foreign Minister Sheikh Khaled al-Khalifa, in an annual consultation to examine key issues and ways of boosting cooperation.