Palestinians gather around the remains of a bus that was hit in an Israeli missile strike in Gaza City
The military confirmed it launched the missile strike on Hamas militants hiding out near the West Bank town of Salfit.
Earlier in the day Israeli helicopters fired missiles at Hamas targets in Gaza, including a van carrying militants and homemade rockets. Four militants were killed in the strike and at least five other people were injured.
The Israeli air strikes in Gaza followed a night of rocket and mortar attacks by Palestinian militants on Israeli targets. One attack killed a woman at a communal farm just outside the Gaza Strip.
Militants continued to fire mortars and rockets at Israeli targets throughout the day Friday.
The missile strikes signal a resumption of Israel's controversial policy of targeted killings of militant leaders, a practice it suspended after the truce agreement with the Palestinians in February.
Gun battles also raged early Friday between Palestinian security forces and Hamas members in Gaza City. The fighting erupted Thursday night when Palestinian police moved in to stop militants from launching more rocket attacks. Two Palestinian teenagers were killed in the fighting.
Chief Palestinian negotiator, Saeb Erekat, told VOA that Hamas is to blame for the intra-Palestinian violence in Gaza. But, he said the Israeli action is not helpful.
"At a time when we are trying to sort these things out, we see the Israelis poking their noses [in], firing, complicating our lives further," he said.
The fighting comes as Palestinian Prime Minister Mahmoud Abbas is in Gaza to meet with militant leaders.