(CNN) -- As attackers target reporters and governments shut down television stations, Latin America ranks among the most dangerous regions for journalists, according to an Amnesty International report released Friday
Nearly 400 journalists were threatened or attacked in the Americas in 2010, and at least 13 were killed by unidentified assailants, the human rights organization said in its annual report.
"In many cases, those killed were believed to have been targeted because of their efforts to uncover corruption or to expose the links between officials and criminal networks," Amnesty International's annual report says.
Mexico is one of the worst offenders, said Javier Zuniga, a special adviser on human rights at Amnesty International.
In that country alone, he said, 11 journalists have been killed since the beginning of 2010.
"It's a sense of impunity that feeds into more killings and more abuses throughout the continent, especially in Mexico, Colombia, Honduras and Brazil," he said.
Amnesty International's report also cites Venezuela and the Dominican Republic, where the organization said government officials shut down "a significant number of TV stations."
Over the past week, press freedom advocates have highlighted several incidents in the region.
On Wednesday, the Committee to Protect Journalists called on authorities to investigate the killing of a Honduran journalist who was reportedly shot in the back outside his home this week.
Cable television host Hector Francisco Medina Polanco had been threatened several times over the past six months as he reported on corruption in the local mayor's office and regional land disputes, the New York-based organization said.
"It is unacceptable that Medina Polanco had reported being threatened and was not given protection," CPJ Deputy Director Robert Mahoney said in a statement.
Ecuador's government also drew criticism from the organization last week as voters across the country headed to the polls for a referendum on proposals that included the creation of a council to regulate media content. Another controversial proposal would prevent media owners and their shareholders from owning stock in any company outside of that industry.
Ecuadorian President Rafael Correa has said that if approved, the measure would prevent conflicts of interest, but others see it differently.
"We believe the referendum questions are aimed at stifling voices that oppose your administration," CPJ Executive Director Joel Simon wrote in a letter to Correa.
Correa has said all 10 referendum proposals passed, but authorities were still counting votes Thursday.
In a visit to Argentina last week, a delegation from the Inter American Press Association accused the South American country's government of cracking down on press freedom.
Argentinian President Cristina Fernandez de Kirchner spearheaded a controversial audio-visual communication policy in 2008 that critics said was aimed at hobbling the holdings of the Clarin media company. Fernandez has accused Clarin of unfairly criticizing her administration.
But the implications of Latin America's struggle over press freedom could stretch far beyond the region's borders, Amnesty International's Zuniga said.
"The Americas should be a lesson for what might happen in the future in the Middle East and North Africa," he said.
Even though military regimes collapsed in many Latin American countries, he said, "the culture of impunity and repression remained."
CNN's Catherine E. Shoichet and Javier Doberti contributed to this report.