Story highlights Israel views drone flyover "very severely," Defense Minister Ehud Barak says

Israeli officials don't know where the drone came from, a spokeswoman says

The drone did not carry any weapons or explosives

The Israeli air force shot down an unmanned drone Saturday over the northern Negev desert, the nation's military said.

The Israeli Defense Forces spotted the drone, which did not carry any weapons or explosives, hovering over Gaza before it entered Israeli airspace, military spokeswoman Avital Leibovich said.

Forces kept the drone under surveillance until a fighter jet shot it down around 10 a.m. Saturday over the Yatir Forest, the IDF said.

Leibovich declined to discuss the drone's route or whether it had flown over military installations.

"We view this incident of attempting to enter Israeli airspace very severely and we will consider our response later," Israeli Defense Minister Ehud Barak said in a statement released Saturday afternoon.

It was not clear where the drone originated. Military officials, however, said it does not appear that it took off from Gaza, which along with Egypt's Sinai Peninsula and Mediterranean Sea forms the western border of the Negev.