Under the terms of the truce, Israel will ease its blockade on Gaza and talks to release an Israeli soldier held by Hamas are expected to resume.
Israeli PM, Ehud Olmert, has warned that the truce, which started at 0600 (0300 GMT), will be fragile.
At least 40 rockets and mortars were fired from Gaza at Israel on Wednesday and Israel carried out air strikes.
Another militant group, Islamic Jihad, who lost several members to Israeli air strikes in recent days, claimed responsibility for some of the attacks.
The United States on Wednesday expressed hope that the Gaza ceasefire deal between Israel and Hamas would force the militant group to "give up terrorism."
"We hope this means no more rockets will be fired by Hamas at innocent Israelis as well as lead to a better atmosphere for talks between Israel and the Palestinian Authority," said U.S. National Security Council spokesperson Gordon Johndroe.
"We appreciate Egypt's efforts and hope they are ultimately successful, but for that to happen, Hamas has to choose to become a legitimate political party and give up terrorism. They can't continue to do both," he said.
Israel on Wednesday officially confirmed an Egyptian-brokered truce with Hamas-led Palestinian militant groups in the Gaza Strip, starting at 6:00 a.m. (0300 GMT) Thursday