Palestinian terrorists in the Gaza Strip fired a rocket at Israel late Monday, the army said, without reporting any casualties or damage.
Sirens sounded in areas of southern Israel neighboring Gaza to warn of the incoming fire, for which there was no claim of responsibility.
The army said the projectile likely fell in an open area.
Hours later, the army said an Israel Defense Forces aircraft struck a Hamas military installation in the southern Gaza Strip in retaliation for the rocket fire. There were no immediate reports of casualties.
The last cross-border rocket attack, after which Israel retaliated with air raids, came on September 15 and coincided with the signing in Washington of normalization deals between the Jewish state and the United Arab Emirates and Bahrain.
A truce mediated by Qatar has since held.
During the previous barrage last month, 15 rockets were fired from the Gaza Strip at Israel, one of which struck the city of Ashdod, injuring two people. Most of the rockets were intercepted by the Iron Dome system, the Israel Defense Forces said.
That rocket-fire represented the first attacks since an unofficial ceasefire agreement was reached between Israel and terror groups in the Strip late August and the largest barrage since February. It drew retaliatory strikes from Israel.