JERUSALEM - Israel yesterday launched an unusually heavy series of airstrikes on Gaza in retaliation for Palestinian rocket attacks, raising the prospect of a new round of bloody fighting after a relative lull for two years.

The military said the Israeli strikes hit seven different targets in Gaza. Palestinian officials said eight militants were wounded. Then the Palestinians fired another rocket at southern Israel, lightly wounding a 16-year-old Israeli girl.

The violence followed the deaths of five Gaza militants Saturday in the deadliest Israeli assault on the coastal strip in months, indicating a trend of escalation. Two years ago, incessant rocket barrages from Gaza led Israel to launch a punishing three-week invasion that left more than 1,400 Palestinians dead, including many civilians.

In another sign of increasing tension, the Israeli military chief, Lt. Gen. Gabi Ashkenazi, said yesterday's strikes were the first to target Gaza's ruling Hamas since the invasion. The military said the attacks were in response to the firing of 13 rockets and mortars at Israel over the past week.

Appearing before parliament's foreign affairs and defense committee, he described the situation as potentially "fragile and explosive."

Until recently, militant attacks from Gaza had subsided dramatically since Israel's offensive in late 2008,

Although Hamas, the Islamic militant group that rules Gaza, has limited attacks on Israel since then, Israel holds the group responsible for all attacks from the territory. A number of smaller militant groups have continued to fire rockets and mortars.

The military said yesterday's airstrikes targeted a weapons factory and smuggling tunnels.