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Suspicious devices have been found in packages mailed to Barack Obama, Hillary Clinton, and CNN’s New York City offices, the Secret Service said today. Suspicious packages were also found near the offices of Democratic lawmakers Debbie Wasserman Schultz in Florida, and Kamala Harris in California, prompting evacuations. The FBI said the packages appeared to contain pipe bombs.

These alarming discoveries follow reports on Oct. 22 of an explosive device found in the mail addressed to philanthropist George Soros. No one has been reported hurt by the intercepted packages.

Terrorism has been rising in the US, driven by a surge of attacks motivated by right-wing ideologies. However, authorities have yet to identity who’s behind the suspicious devices found this week.

A rise in right-wing terror

An analysis of the Global Terrorism Database by researchers at the University of Maryland published in 2017 shows a “sharp increase” in the share of attacks by right-wing extremists, from 6% in the 2000s to 35% in the 2010s. The share of attacks by religious extremists also increased, from 9% to 53% between the two decades.

Meanwhile, the share of attacks by left-wing terrorists and environmentalist extremists dropped from 64% in the 2000s to 12% in the 2010s.

Researchers point out that many recent attacks on US soil are carried out by individuals without any strong links to a terrorist organization—known popularly as “lone wolves.”

The study defines “right-wing extremism” as “violence in support of the belief that personal and/or national way of life is under attack and is either already lost or that the threat is imminent,” including anti-globalism, white supremacy, nationalism, suspicion of the government, and beliefs in conspiracies.

An analysis by Quartz of the same Global Terrorism Database confirmed that the trend persisted in 2017, when most attacks in the US were committed by right-wing extremists. Out of 65 incidents last year, 37 were tied to racist, anti-Muslim, homophobic, anti-Semitic, fascist, anti-government, or xenophobic motivations.

That list includes an attack by neo-Nazi extremist James Fields against a crowd of counter-protestors in Charlottesville, which left one person dead. It also includes attacks against a gay bar in Puerto Rico, mosques in Washington, Texas, and Florida, and a vehicle decorated with Jewish iconography in New York.

In the same period, seven attacks were linked to Islamic extremists, and 11 attacks were inspired by left-leaning ideologies.

That right-wing activity is fueling a surge in terrorism in the US. Overall, the US had only six attacks a decade ago, but 65 in 2017. The number of fatalities is also increasing, in contrast to a global decrease in terror attacks.

Terror attacks around the world fell from about 17,000 in 2014 to about 11,000 in 2017. They dropped almost 40% in the Middle East.