Ethiopian authorities have arrested nine journalists and bloggers on allegations that they worked for foreign human rights groups or used social media to incite violence, sources told the International Press Institute (IPI) today, saying they feared additional detentions.

IPI condemned the arrests, which targeted some individuals who met with the organisation’s representatives during a press freedom mission to the country in November 2013, and reiterated calls for the government to respect freedom of the press and access to information.

“The Ethiopian authorities seem determined to crush any independent source of information, be it in print or online, and local, regional and international press freedom groups have so far failed to halt the ongoing harassment,” IPI Press Freedom Manager Barbara Trionfi said. “There needs to be concerted international pressure from Ethiopia’s donors and partners, including the European Union and the United States, to end the abuse and to pressure the Ethiopian leaders to respect their constitutional and international obligations to respect fundamental rights of media freedom.”

The arrests came three days before U.S. Secretary of State John Kerry is due to arrive in the Horn of African nation on a visit “to advance peace and democracy”, a State Department spokesperson announced Friday. That announcement came the same day that the State Department kicked off a campaign to promote media liberty in conjunction with World Press Freedom Day on May 3.

Nine Ethiopians – three of whom worked for Amharic and English newspapers and others who wrote for the dissident Zone 9 blog – were reportedly arraigned in an Addis Ababa court on Sunday, a day after their arrest.

The editor of one newsweekly confirmed the arrests in a telephone interview with IPI. The editor said the nine are still being held at the central police jail in Addis Ababa and have been denied access to lawyers, family and colleagues. In an earlier e-mail about the arrests, the editor commented: “We don’t know what tomorrow holds for the rest of us.”

Other journalists contacted by IPI confirmed the arrests but declined to comment, citing fear of detention by the security services.

The Zone 9 blog is blocked in Ethiopia and had not been updated for months. However, its contributors recently announced they would resume publishing the blog, which is accessible outside Ethiopia, raising speculation that the authorities would crack down on those involved. It was not immediately clear why the three working journalists were arrested, although the editor of the newsweekly told IPI they were close associates of the blog’s contributors.

The arrests were announced on the Twitter feed of the Zone 9 group and its Facebook page said the nine Ethiopians were arrested “on charges of ‘working with foreign human right activist organisations’ … and ‘inciting violence through social media to create instability in the country.’ ” Zone 9 contributors, who include business people and academics as well as a former journalist, have remained active on social media, often accusing the Ethiopian government of human rights violations and repressing dissent.

The Addis Standard reported today that those arrested included its own writer Tesfalem Weldyes, who also contributes to the independent Addis Fortune business weekly; Asmamaw Haile Giorigis, who works for the Addis Guday magazine; and Edom Kassaye, a former journalist with the state-run Addis Zemen newspaper, who is part of the Zone 9 group.

The other Zone 9 bloggers reported arrested were Mahlet Fantahun, Abel Wabela, Befeqadu Hailu, Zelalem Kebret, Atenaf Berahene and Natnael Feleke.

Two of those jailed, Edom Kassaye and Mahlet Fantahun, are women.

In a report issued following its 2013 press freedom mission, IPI said that Ethiopia’s frequent arrests of journalists and use of anti-terrorism law to imprison reporters and editors are hindering the development of free and independent media in Africa’s second largest country.

Dozens of journalists and political dissidents have been arrested or sentenced under the Anti-Terrorism Proclamation of 2009, including five Ethiopian journalists who are serving prison sentences and who at times have been denied access to visitors and legal counsel. The report, “Press Freedom in Ethiopia”, was based on a mission to the country carried out in November by IPI and the World Association of Newspapers and News Publishers (WAN-IFRA).

The report calls on the Ethiopian government to free journalists convicted under the sedition provisions of the 2009 measure. These journalists include Solomon Kebede, Wubset Taye, Reyot Alemu, Eskinder Nega and Yusuf Getachew. Mission delegates were barred access to the journalists, who are being held at Kaliti Prison near the capital Addis Ababa.

The report also urges the 547-member lower house of parliament to revamp the anti-terror law to ensure that it does not trample on the rights of freedom of speech and assembly provided under Article 29 of the Ethiopian Constitution and further guaranteed under the African Charter on Human and People’s Rights and the U.N. Human Rights Covenant, which Ethiopia has ratified.

Last week, at their World Congress in South Africa, IPI members adopted a resolution sharply criticising the Ethiopian government for its use of anti-terror laws against journalists.

The “broad application of anti-terror measures against journalists impinges on fundamental rights – including freedoms of the press and expression, and access to information – that are guaranteed under the nation’s Constitution as well as on its obligations under United Nations and African Union treaties,” the IPI resolution said.

“The use of the laws in Ethiopia to arrest and detain, in some cases without formal charges, have fuelled a sense of fear among media workers, both foreign and domestic.”