Since taking control of the Gaza Strip in 2007, Hamas has adopted the rocket tactics used by Lebanese Hezbollah, shifting away from its reliance on suicide bombers in attacks on Israel.
Part of that shift may be attributable to Hamas' arsenal of longer-range rockets. Several Israeli towns that had previously been out of reach of Hamas' rockets now are being hit by them.
Hamas rockets have struck the large southern cities of Beersheba and Ashdod, home of Israel's largest port, for the first time since the militant group broke its cease-fire with Israel on Dec. 19.
A former U.S. intelligence official said Hamas is now using Iranian versions of the Katyusha and Grad rockets with a range of 18.6 to 21.7 miles. The new rockets dramatically extend Hamas' reach.
Hamas, which is labeled by the United States and several other Western nations as a terrorist organization, had relied heavily on the shorter-range homemade Qassams that fly only up to 1.8 miles, the former official said. He spoke anonymously in order to discuss Israeli intelligence.
The rockets do not have guidance systems so are indiscriminate in targeting. But that makes them well suited for a barrage on a town or a dispersed battlefield of soldiers, particularly if fired in great numbers.
National Security Council spokesman Gordon Johndroe on Wednesday told reporters in Crawford, Texas, that "there is no doubt" both Iran and Syria are supplying Hamas with weapons. Iran has long been suspected of providing financial support to the militant Palestinian group.
A U.S. counterterrorism official, however, said many of Hamas' rockets are cobbled together in a rudimentary way by militants in Gaza from parts smuggled into the region. The official, who declined to discuss numbers, spoke on condition of anonymity to discuss foreign intelligence.
In the monthlong 2006 conflict with Israel, Lebanese Hezbollah fired more than 4,000 missiles into Israel, about a third of its missile stores at the time. Most were Katyusha-type rockets, which are quick to set up and have ranges of about 12 miles.
The Israeli government said in 2006 that Hezbollah also wielded Iranian-made missiles with ranges of up to 50 miles.
Hamas does not appear to have used those longer-range tactical missiles.
Four Israelis have been killed by Hamas' rocket fire in recent days, including three civilians, since the cease-fire broke on Dec. 19.
Gaza officials say Israel's retaliatory airstrikes have killed about 390 and wounded about 1,600. Hamas says some 200 uniformed members of Hamas security forces have been killed. The U.N. says at least 60 Palestinian civilians have died.