Terrorist attacks in the Western Hemisphere were up almost 40 percent from 2010-2011, driven by Colombian guerrilla groups that have stepped up hit-and-run offensives even as they’ve seen their forces decimated, the U.S. Department of State reported Tuesday in its annual Country Reports on Terrorism.

The vast majority of the hemisphere’s 480 terrorist attacks could be attributed to the Revolutionary Armed Forces of Colombia, or FARC, and the smaller National Liberation Army, or ELN.

“We know that it takes a long time for terrorist groups to be truly wound down and put out of business,” Daniel Benjamin, with the Office of the Coordinator for Counterterrorism told reporters, referring to Colombia’s almost half-century long conflict. “So if there are continuing attacks, I suppose that shouldn’t be a surprise. But again, we consider Colombia to be a success case and one in which its leadership showed great resolve.”

The study also cited neighboring Venezuela for not fully cooperating with U.S. counter-terrorism efforts. The nation has repeatedly been accused of turning a blind eye to FARC operations along its remote and porous border with Colombia. Last year, four Venezuelan officials, including current Defense Minister Henry Rangel, were designated under the U.S. Treasury’s Foreign Narcotics Kingpin act for supporting the FARC’s drugs and arms trafficking activities.

The report also highlights the growing influence of Iran in the region.

“The most disturbing manifestation of this,” was an alleged Iranian plot to assassinate the Saudi Ambassador to the United States by enlisting members of a Mexican cartel, the report found. The potential cartel hit men were actually U.S. government informants and the plot was thwarted in October.

Cuba, which was declared a state-sponsor of terrorism in 1984, continues harboring U.S. fugitives and members of the Basque separatist group ETA. But “there was no indication that the Cuban government provided weapons or paramilitary training for either ETA or the FARC,” the report found.

While there were no known al Qaeda or Hezbollah cells in the hemisphere, the study said that sympathizers in South America and the Caribbean continued to provide financial and ideological support to the groups.

Globally, the study found there were more than 10,000 terrorist attacks in 70 countries last year, resulting in over 12,500 deaths.