Air raid sirens sounded in Tel Aviv on Friday and an explosion was heard, witnesses said, and Hamas militants in the Gaza Strip said they had fired a rocket at Israel's commercial centre.

A police spokesman acknowledged an explosion had been heard but said there was no initial indication a rocket had struck the city nor any immediate reports of casualties or damage.

The armed wing of the Islamist Hamas movement said it had fired a Qassam rocket at Tel Aviv.

Palestinian militants in Gaza launched two rockets toward the city on Thursday. One fell in the sea, a security source said, and the other landed in a Tel Aviv suburb, causing no damage or casualties.