Two multistory houses took direct hits when a five-rocket salvo exploded on an Ashdod residential street Saturday afternoon. Seven people were injured and 15 went into shock. A truck caught fire. Several other buildings were damaged. In the Eshkol district, two houses were hit by rockets after four soldiers were taken to hospital with injuries.   Dozens of rockets also struck Ashkelon, Beer Tuvia, Netivot and Beersheba. A fifth Iron Dome battery has been stationed in the Tel Aviv area. It is also designed to defend Jerusalem against missiles attack.