Israeli aircraft struck at least four targets in the Gaza Strip today, a day after a rocket fired from the Palestinian enclave killed a Thai worker in Israel, Hamas security officials and witnesses said.

There were no immediate reports of injuries in any of the strikes, whose targets included a smuggling tunnel along the border with Egypt, two open areas in Khan Younis and a metal foundry near Gaza City.

The Israeli military had no immediate comment.

Vice Prime Minister Silvan Shalom had said Israel would make a strong response to what was the first deadly rocket fire from Hamas-ruled Gaza at Israel in more than a year.

Israel also sent a letter of complaint to U.N. Secretary General Ban Ki-moon, who is due to visit Israel at the weekend, and the U.N. Security Council.

Israel's U.N. Ambassador Gabriela Shalev urged Ban to call for the release of Israeli soldier Gilad Shalit, captured by Gaza militants in 2006. Hamas has demanded Israel free hundreds of the thousands of militants in its jails in exchange for the soldier.

A previously unknown group, Ansar al-Sunna, believed to share the hardline ideology of al Qaeda, claimed responsibility for the rocket fire at Israel, as well as the Al-Aqsa Martrys Brigades, a wing of the mainstream Fatah movement.

Hamas Islamists, who took control of the Gaza Strip in 2007, had been urging other militant groups not to strike Israel, voicing concern about possible Israeli retaliation.

Palestinian militants in Gaza have carried out sporadic rocket and mortar bomb attacks on Israel since the end of a three-week Gaza war in January 2009, usually without causing any casualties.

More than 1,400 Palestinians, including hundreds of civilians, were killed in that offensive, launched with the declared aim of curbing rocket attacks. Thirteen Israelis, among them three civilians, were killed.