Israeli aircraft bombed targets in southern Gaza after dark on Tuesday in response to a rocket attack which hit the Israeli port city of Ashkelon earlier in the day.
There were no reports of casualites from either strike.
Israeli warplanes struck at smuggling tunnels connecting Gaza with Egypt and fired a missile at a training camp of the armed wing of the Islamist Hamas movement, which rules the enclave.
Israeli Prime Minister Ehud Olmert had warned Hamas of a harsh response to any further rocket fire from Gaza, although the country's defence minister, Ehud Barak, has said he does not foresee a new all-out offensive.
Both sides ordered ceasefires on 18 January after Israel's devastating 22-day offensive in Hamas-run Gaza, in which 1,300 Palestinians were killed including more than 700 civilians.
Eleven Israeli soldiers and three civilians have been killed since the conflict erupted in late December.
Israel has carried out air strikes but held back from a renewed ground offensive during a surge of violence, in which three Palestinian civilians and a gunman were killed.