Palestinian resistance fighters in Gaza have launched rockets that have landed near sensitive installations outside the southern Israeli city of Ashkelon in recent weeks, including a power plant and fuel depot.

Menachem Nechama, director of Mekorot Water's southern division, said no rockets have fallen near the company's installation near Ashkelon, but preventively, the company has begun using the more expensive liquid hypochlorite instead of chlorine gas to disinfect the water supply.

"If chlorine gas is hit in a terror attack, it is environmentally toxic," Nechama said. "If liquid hypochlorite is hit, it spills into the ground." He said that this causes only limited, short-term damage.

German soldiers used chlorine gas during the first world war in trench warfare against the French, Nechama said.

Depending on the dosage, exposure to chlorine gas can cause lung damage, and in extreme cases, death. If hypochlorite  were to spill, "then I imagine in that place, plants won't grow for several weeks", but there would be no other effect, he said.