A joint statement issued from the office of Catherine Ashton, the European Union's foreign policy chief, and Neighborhood Commissioner Stefan Fule said there was concern about the state of political freedom in Azerbaijan.
"The EU notes with concern the continued pressure on a number of opposition activists, civil society and independent media, such as intimidations, arrests on dubious charges, detentions and sentencing without proper respect for international standards and rights of the accused," their Thursday statement said.
Azerbaijan holds presidential elections next week.
British advocacy group Index on Censorship said suppression has extended to the social media landscape, where local activists say "liking" someone's status on Facebook is considered controversial.
The Index said Azeri legislators starting adopting "regressive legislation" in May in an effort to crack down on voices seen as insulting to the government.
"As [President Ilham Aliyev's administration] tightens the screws, space for free expression is shrinking and prospects for free and fair elections grow slimmer," the campaign group said.
Aliyev took office in 2003.