A public affairs division of the U.S. Department of Defense has apologized and deleted a tweet that appeared to threaten to kill civilians who had been drawn to a secretive military base in Nevada rumored to house government secrets about extraterrestrial life and spaceships.

"Last night a DVIDSHUB employee posted a Tweet that in NO WAY supports the stance of the Department of Defense. It was inappropriate and we apologize for this mistake," the division wrote Saturday in a tweet from its official account.

Prompted by a Facebook post inviting people to "Storm Area 51," UFO enthusiasts had poured into rural Nevada on Friday near the base, known colloquially as Area 51, but fears of a mass raid on the remote site or a public safety crisis proved unfounded, with just three people arrested.