WASHINGTON, D.C. - The federal government will require many drone aircraft to be registered, a move prompted by the growing number of reported close calls and incidents that pose safety risks, officials announced Monday.

Pilot sightings of drones have doubled since last year, including sightings near manned aircraft and major sporting events, and interference with wildfire-fighting operations, the government said at a news conference to announce the step. As first reported by CBS News, a record of at least 650 drone sightings have been reported by pilots so far this year. That's compared to 238 in all of 2014.

"These reports signal a troubling trend," Federal Aviation Administration chief Michel Huerta said in a statement. 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."

To work out details, the FAA and the Transportation Department are setting up a 25- to 30-member task force including government and industry officials and hobbyists. They'll recommend which drones should be required to register and which should be exempted, and design a system that would be easy for commercial operators to comply with, the department said.

Toys and small drones that don't present a safety threat are likely to be exempt. Drones that weigh only a pound or two or that can't fly higher than a few hundred feet are considered less risky. Heavier ones and those that can fly thousands of feet pose more of a problem. Currently, drones are considered hobby aircraft and are exempt from registration because they are supposed to be operated below 400 feet.

There is no official count of how many drones have been sold in the U.S., but industry officials say it is in the hundreds of thousands and will easily pass a million by the end of the year.

The Associated Press contributed to this report.