WASHINGTON — Concerned about rising reports of close calls and safety risks involving drones, the government announced Monday it will require many of the increasingly popular unmanned aircraft to be registered.

Pilot sightings of drones have doubled since last year, including near manned airplanes and at major sporting events, and there are reports of interference with wildfire fighting operations, Transportation Secretary Anthony Foxx said at a news conference.

“These reports signal a troubling trend,” said Federal Aviation Administration chief Michel Huerta. Registration will increase pressure on drone operators to fly responsibly, he said, adding, “When they don’t fly safely, they’ll know there will be consequences.”

The FAA now receives about 100 reports a month from pilots who say they’ve seen drones flying near planes and airports, compared with only a few sightings per month last year. So far there have been no accidents, but agency officials have said they’re concerned that a drone weighing only a few pounds might cause serious damage if it is sucked into an engine or smashes into an airliner’s windshield.

Toys and small drones that don’t present a safety threat are likely to be exempt from the requirement. Drones that weigh only a pound or two or that can’t fly higher than a few hundred feet are considered less risky, but heavier ones and those that can fly thousands of feet pose more of a problem.

To work out details, the FAA and the Transportation Department are setting up a task force including government and industry officials, pilots and hobbyists. They’ll recommend which drones should be required to register.

It’s hard to identify drones seen operating illegally near airports and planes or over crowds, and registration by itself won’t change that. But it would allow the FAA to identify drones when they can be recovered after landing or crashing, a common occurrence.

Earlier this year, drones operated illegally crashed on the White House lawn and at the New York stadium where the U.S. Open Tennis Championships were being held. In both cases the drone operators came forward. But if they hadn’t, the government would have had no way to identify them.

“There can be no accountability if the person breaking the rules can’t be identified,” Foxx said.