Israel aircraft have bombed a Palestinian target in Gaza, following Palestinian militant rocket attacks on Israel on Sunday.
The Hamas militant group that runs Gaza says Israeli aircraft hit a Palestinian police position.
On Sunday, Palestinian militants fired at least seven rockets and mortar shells into Israel, drawing an Israeli threat of a "disproportionate" response.
Israeli police say the projectiles wounded two people in southern Israel. Israeli Prime Minister Ehud Olmert warned that Israel will retaliate severely for cross-border attacks that he says deprive Israelis of a normal life.
Palestinians in southern Gaza reported receiving recorded phone messages warning them to immediately evacuate areas housing smuggling tunnels and weapons stockpiles.
Rockets have struck Israel sporadically since it ended a three-week offensive against Hamas militants controlling Gaza last month. Israel has carried out several airstrikes on Gaza militants in response.
Exiled Hamas leader Khaled Meshaal ruled out any permanent cease-fire with Israel during a visit Sunday to Tehran.
Hamas has demanded that Israel open its border crossings with Gaza as part of a truce. Israel says that will not happen until Hamas releases an Israeli soldier held captive in Gaza since 2006.
Meshaal thanked Iran for, as he put it, playing a major role in what Hamas considers to be its "victory" against Israel in the recent fighting. Israel accuses Iran of providing weapons to Hamas, but Tehran says its support of the group is only political.
Meshaal met with Iran's Supreme Leader Ayatollah Ali Khamenei, who praised Hamas for resisting Israel and urged the group to be prepared for another Israeli assault.
Egypt has begun installing surveillance cameras and motion sensors on its border with Gaza as part of efforts to crack down on tunnels used by weapons smugglers. Israel bombed the tunnels during its three-week offensive against Hamas.