Palestinian witnesses say an Israeli helicopter has fired into Gaza City, killing three people including at least one Hamas militant.
They say a missile hit the Gaza neighborhood of Zeitoun, which was recently the scene of fighting between Israeli forces and Palestinian militants.
The Israeli military has not commented on the reported operation.
On Saturday, Israeli forces shot and killed a suspected Palestinian militant near the border fence between Israel and the Gaza Strip.
An in the West Bank, an Israeli army captain was killed in a clash with Palestinian militants in a refugee camp near Nablus. The radical al-Aqsa Martyrs Brigade, a militant group linked to Palestinian leader Yasser Arafat's Fatah movement, claimed responsibility for the killing.