GAZA, Feb 2 (Reuters) - Israel launched air strikes in the Gaza Strip on Tuesday hitting tunnels along the border with Egypt and an abandoned airport, officials on both sides said.

There were no reports of injuries from what witnesses said were five missiles fired by Israeli air force fighter jets at an airport is not operational and on tunnels Israel says are used to smuggle weapons into the coastal territory.

An Israeli army spokesman confirmed the attacks took place saying the air strikes targeted two sites where tunnels were dug to help gunmen infiltrate from Islamist Hamas-ruled Gaza into Israel and to smuggle in weapons from Egypt.

The strikes were in response to two explosive devices that washed up on Israel's coastline the previous day, and rockets fired at Israel, including one that slammed into a farming area on Tuesday causing no injury, the Israeli spokesman said.

The attacks came shortly after Israeli Prime Minister Benjamin Netanyahu told a news conference alongside Italy's Prime Minister Silvio Berlusconi that Israel would respond to the explosives found on the country's Mediterranean beaches.

Palestinian militants from the Israeli-blockaded territory claimed responsibility for what Israel described as an unusual type of attempted attack. Most attacks from Gaza in the past few years have been by rocket shootings at Israeli towns.

The Islamic Jihad group said it had floated the explosives out to sea in a joint operation with two other groups including the al-Aqsa Martyrs Brigades of Palestinian President Mahmoud Abbas's Fatah movement.

Hamas, a Palestinian group that seized control of Gaza in 2007, has largely reined in its own militants since a devastating war with Israel a year ago in which 1,400 Palestinians and 13 Israelis were killed.

In a separate development, an Arab resident of an Israeli town was spotted wandering toward the Gaza border, an Israeli military official said. The same man has made previous attempts to illegally cross into Egypt and Jordan, and was believed to be mentally unstable, the official added.

Palestinian witnesses said Hamas police officials took the man into custody after he crossed into Gaza. There were no further details immediately available about the case. (Reporting by Nidal al-Mughrabi; Writing by Allyn Fisher-Ilan; Editing by Jon Hemming)