JERUSALEM (Reuters) - Iran's missile attack on Tuesday was serious and will have consequences, Israel's military spokesperson said, declining to specify how and when Israel would respond.

Rear Admiral Daniel Hagari said he was not aware of any casualties from the missile volley. He said there were a few hits in the centre of the country and in the south.

"We are on high alert both defensively and offensively," Hagari said in a TV broadcast. "We will defend the citizens of the State of Israel. This attack will have consequences. We have plans, and we will operate at the place and time we decide."

Iran fired a salvo of ballistic missiles at Israel on Tuesday in retaliation for Israel's campaign against Tehran's Hezbollah allies in Lebanon. Alarms sounded across Israel and explosions could be heard in Jerusalem and the Jordan River valley after Israelis piled into bomb shelters.

(Reporting by Steven Scheer; Editing by NMark Heinrich and Lisa Shumaker)