Israeli aircraft have fired missiles at targets in Gaza as part of an operation against Palestinian militants.
Israeli troops are massed around the perimeter of the Gaza Strip
Three bridges were hit in the northern Gaza Strip which the army said were being used by militants to reach an area where they stage rocket attacks.
A second strike in Khan Younis hit a building used by a money-changer, who Israelis say is linked to Hamas.
A military spokesman also confirmed the arrest of 82 alleged militants in the West Bank overnight.
Reports say Israeli forces have detained more than 300 suspects in raids in the last three days.
A Palestinian security official said one person was slightly wounded in the overnight strike on Khan Younis which flattened the money-changer's office.
Locals said the man was from the mainstream Fatah faction rather than the Hamas militant group.
Israel launched an offensive against Palestinian militants over the weekend after rockets were fired from Gaza at Israeli towns nearby.
Defence Minister Shaul Mofaz said he was "not satisfied" with a pledge by the militant group Hamas to halt rocket attacks.
The latest round of strikes have killed four Palestinian militants
He said that whatever Hamas announced, it was secretly pressing other militant groups to launch attacks.
"We will not allow them to continue with that policy," he said.
He also said Israel would continue with what it calls the targeted killings of leaders of Palestinian militant groups.
The controversial policy has been one of Israel's main strategies against Palestinian militant leaders.
Palestinian spokesman Nabil Abu Rudeina warned Israel against continuing raids and assassinations in Gaza.
"Continued assassinations will explode the entire situation. We are asking the international community, especially the US, to move immediately and put strong pressure on Israel to stop this," he said in an interview with AFP.
Hamas said it had been retaliating for an explosion at a Hamas rally that killed 15 people on Friday. Israel denies involvement.
"They killed innocent Palestinians during a parade on Friday and then accused Israel. And in order to back up this lie, they fired dozens of Qassam [rockets]... and wounded Israeli civilians. We will not let this pass," Mr Mofaz said.