Gaza militants fired into southern Israel on Tuesday, hours after the death in custody of a Palestinian who suffered from cancer, witnesses and the Israeli military said.
Witnesses told AFP that militants in Gaza City had fired three mortar rounds towards Israel, but the army said only one projectile had landed in the Jewish state, without causing any casualties.
A military spokeswoman told AFP it was not immediately clear if it was a rocket or a mortar shell.
There was no claim of responsibility from the Palestinian side.
The death on Tuesday morning of Maisara Abu Hamdiyeh, a 63-year-old prisoner from Hebron who had been suffering from throat cancer, sparked Palestinian anger with officials blaming Israel for allegedly refusing to release him early on compassionate grounds.
Hamas spokesman Sami Abu Zuhri told AFP that the faction was watching the developments with "the greatest concern" and that Israel would "regret its continuing crimes".
It was the third instance of rocket fire since the end of a deadly eight-day confrontation between Israel and Hamas militants in November which ended with an Egyptian-brokered truce that has been almost completely respected.
The last time rocket fire hit Israel was on March 21 during a visit by US President Barack Obama, when two rockets landed causing some damage but no injuries.