Human Rights Watch calls rocket attacks by Palestinian fighters “unjustifiable”.
“We aren’t ready to accept rocket fire at our communities,” he said on Monday.
Two mortar rounds were fired at Israel’s Erez border crossing with Gaza a day earlier, exploding 300 metres from the border, but not injuring anybody.
A rocket was also fired from Gaza on Saturday, exploding in open ground on the Israeli side of the border.
It is not clear who fired the rockets, but some small fighter groups in Gaza say Hamas has been trying to stop them firing at Israel, which controls the delivery of fuel and food aid to the territory.
But such raids by Israel have occurred less frequently recently, with Monday’s attack the first of its kind in two months.
Hamas has been calling on Israel to lift its blockade and open the border crossings, but Israel says Hamas must first release captured Israeli soldier Gilad Shalit, whom it has held for three years.