WASHINGTON (Reuters) - The FBI, focused intently for years on combating terrorism from abroad, is turning more attention to home-grown, U.S. domestic violent extremists, a senior FBI counterterrorism official said on Thursday.

Arrests related to domestic terrorism in the current fiscal year, which began on Oct. 1, are at 66, exceeding international terrorism arrests, now at 63.

Terrorism cases are “the FBI’s number one priority,” the FBI official said, noting that every one of the bureau’s U.S. field offices is affiliated with a local “joint terrorism task force” involving both federal and local law enforcement agencies.

While militants linked to international terrorism can be prosecuted under U.S. federal laws introduced after the Sept. 11, 2001 attacks on Washington and New York City, no similar federal laws cover domestic terrorism.

Recent violent extremist attacks in the United States include the killing of 11 people at a synagogue in Pittsburgh last October and a shooting in Kansas in 2017 when an Indian immigrant was killed by an assailant who thought the victim was Middle Eastern.

The figures show international terrorism remains a major focus for the FBI, but the bureau is increasingly treating domestic terrorism as an equally important concern.

The official said domestic terrorism cases relate to racially motivated extremism; anti-government attacks, animal-rights related attacks, and attacks involving abortion clinics or anti-abortion rights protesters.

The internet remains a main source of radicalization for domestic and U.S.-based international terrorists. “Terrorism moves at the speed of the internet,” the official said.

Given the availability of radical messages in cyberspace, the official said, “homegrown violent extremists” - those inspired by foreign movements like Islamic State - now can become self radicalized in just months.

“Attacks inspire attacks,” the official added, noting that attacks such as one against mosques in New Zealand are the type which have inspired or been copied by other attackers.