The air strike in Gaza city early on Friday morning is part of Israel's biggest offensive in Gaza for months, carried out in an attempt to release a captured soldier and to prevent rockets from being fired into Israel.
Hundreds of Palestinians have been killed in the past four months.
With the Friday attacks, 22 Palestinians have been killed since Wednesday when Israeli troops intensified the operation and re-occupied Beit Hanoun in the north of the narrow coastal strip.
One Israeli soldier has also been killed in the operation.
Hamas sources said Friday's aerial missile attack hit a vehicle carrying four men belonging to an elite unit.
The men had stopped near a mosque to pray when their vehicle was hit, witnesses said.
An Israeli military source confirmed an aerial attack on a vehicle.
Imad Mushtaha, a Hamas military leader who had survived previous assassination attempts, was among the dead.
Five people were also wounded in the attack, a medical official said.
A fifth Palestinian was killed by Israeli gunfire in Beit Hanoun on Friday morning.
In other incidents on Friday, two Palestinians, including a woman, were shot and killed by Israeli gunfire.
A medical source said the two were killed while protesting for Israeli troops to leave Beit Hanoun.
Palestinian women running for
cover after Israelis fired at them
The dead woman, whose name was not immediately released, was in her 40s, a hospital doctor in the nearby town of Beit Lahiya said.
A second Palestinian, a male, was killed during a second protest at another entrance to the town, where Israeli troops have been operating since Wednesday.
The doctor also said a second woman was declared clinically dead, and five other women were wounded by Israeli gunfire as a group of women demonstrated at the entrance to Beit Hanoun.
An Israeli army spokeswoman, however, denied that troops operating in the northern Gaza Strip had opened fire at any women.
Israeli troops arrested a Palestinian Cabinet minister in the West Bank town of Ramallah on Friday.
Palestinian security officials identified him as Abd al-Rahman Zidan, the public works and housing minister, from the Palestinians' ruling Hamas party.
Dozens of other ministers and legislators have been arrested in previous Israeli sweeps.
The Israeli army only said that it arrested a Hamas activist.