Twenty Kassam rockets were fired into southern Israel early Monday morning, shortly after the Israeli Air Force struck terrorist targets in the Gaza Strip.

All rockets landed in open areas, mostly in the Eshkol Regional Council, and caused no damage or injuries.

Four rockets landed in open areas in the Sderot, Eshkol and Hof Ashkelon regions after 9 a.m. as fire continued into the morning.

One rocket landed in the Shaar Hanegev Regional Council after dawn. Red alert sirens were heard throughout the area, and residents were advised to stay within 15 seconds of reinforced “secure rooms.”

Earlier Monday, the IAF struck multiple terror targets in Gaza, including two operation centers and a rocket launching site, according to a statement issued by the IDF spokesperson. The strikes were in response to recent rocket attacks, the statement said. Palestinian sources reported that one person was killed.

Seven rockets were fired from the Strip into Israel on Sunday, landing in open fields near the cities of Beersheba and Ashkelon.

School was canceled Sunday for some 40,000 schoolchildren in the area.

On Monday, school resumed in Beersheba.

Last Wednesday, more than 80 rockets and mortars were fired from Gaza, causing damage to eight homes in five Israeli towns and prompting the Cabinet to pass a plan to fortify homes located between 4.5 and 7 kilometers from the border (approximately 3 to 4.5 miles).

According to the Defense Ministry, construction of fortifications for the 26 affected towns will cost an estimated NIS 270 million ($70 million).

The plan is expected to include the installation of 1,629 secure rooms in homes within rocket range at a cost of NIS 250 million, with the rest going for fortification of schools between 7 and 15 kilometers from the Gaza Strip by the end of 2013.

Ilan Ben Zion and Asher Zeiger contributed to this report.