There was no immediate claim of responsibility from Gaza militants for the rocket firing or comment from Hamas, the Islamist armed group that rules the coastal Palestinian enclave.
Hamas has occasionally test-fired rockets, launching them toward the sea. Hamas-affiliated Paltimes news website said, however, that Saturday’s launch was probably a malfunction.
After dark fell, Israel’s military said it struck at “terrorist targets in the Gaza Strip”.
Hamas Radio said some of the group’s security posts and a training camp were struck by Israeli aircraft and tanks. There were no casualties.
In a rare countermeasure, Hamas’s Aqsa TV said militants fired two surface-to-air missiles towards Israeli planes. Israel’s military confirmed that a missile had been launched at one of its planes, which was unscathed.
In Gaza, Hamas spokesman Hazem Qassem blamed Israel for the escalation.
The Israel-Gaza frontier has been largely quiet since an 11-day war in May. But on Wednesday, gunfire from Gaza that wounded an Israeli civilian drew tank fire from the Israeli military, wounding three Palestinians.