Palestinian witnesses say Israeli forces have killed at least four Hamas militants in separate missile attacks in the Gaza Strip and West Bank.
Israel's military did not immediately comment. The attacks Friday come amid a key offensive against Hamas militants in Gaza City.
Earlier, Israeli helicopters launched strikes in Gaza, after Palestinian militants fired missiles into Israel, killing one woman.
Palestinian security forces also launched raids against Hamas militants in Gaza City, sparking clashes that killed two people.
The chief Palestinian negotiator, Saeb Erekat, told VOA that Hamas was to blame for the violence, saying the militants are challenging the authority of elected leaders.
The fighting in Gaza City was the worst among Palestinians since 1994, when police killed more than a dozen Palestinian protesters outside a mosque.
New violence threatens a five-month truce between Palestinians and Israelis as Israel plans to withdraw from Gaza next month.
Information for this report is provided by AP, AFP and Reuters.