Palestinian militants in the Gaza Strip have fired some 565 rockets and 200 mortar shells at southern Israel since the Israel Defense Forces launched its offensive on the Hamas-ruled coastal territory on December 27, the Shin Bet announced on Tuesday.

According to the Shin Bet investigation, some 530 of the rockets were fired within the first 16 days of the operation. The Shin Bet estimated that another 35 were fired over the course of Monday and Tuesday, but did not include those numbers in its latest report.

The report does not detail how many were long-range Katyushas, but various sources estimates they number about 10 percent of the total number of rockets fired.

Some 5,700 rockets and another 4,000 mortar shells have been launched at Israel since the beginning of 2005, the Shin Bet said. Of those, more than 2,000 rockets and 1,600 shells were fired in 2008.

During the six-month truce between Israel and Gaza which ended in December, some 361 rockets and 303 mortar shells were launched at Israel. This marks an average of a rocket and a mortar shell a day over the course of the cease-fire period.

Since the firing began in the year 2000, 19 people were killed by rockets and another 18 by mortar shells.

Some 1,272 people have been wounded by rockets and shells since the beginning of the war on Gaza 18 days ago.

Gaza militants fired 12 rockets and four mortar shells at Israel's southern communities on Tuesday morning, continuing the cross-border attacks that Israel has sought to stop in its offensive against Hamas in the coastal strip.

One of the rockets exploded near a school in Ashkelon. The strike caused minimal damage, but no casualties.

Some of the rockets were fired during a temporary humanitarian cease-fire between Israel and Hamas, imposed daily to allow a free flow of humanitarian aid into Gaza.

Two of the rockets hit open areas in the Sha'ar Hanegev Regional Council, two struck Eshkol Regional Council, and two hit near the town of Ofakim. There were no causalities in the attacks.

On Monday, Gaza militants fired 19 rockets at the western Negev, one of them scoring a direct hit on a home in the coastal city of Ashkelon.

The house's five residents managed to flee to a bomb shelter before the strike, so there were no casualties. A number of people were treated for shock.

Another few rockets were also reported in Sderot and in the central Negev city of Be'er Sheva. Another rocket fired from Gaza exploded in an open field near Kiryat Gat, causing no casualties or damages.

The Israel Defense Forces said Sunday that there has been a dramatic drop in the ability of Hamas to launch rockets at Israel. The launches have dropped by 50 percent compared with the first day of Operation Cast Lead, 17 days ago.