JERUSALEM, August 11, 2008 (AFP) - A rocket fired from the Gaza Strip struck southern Israel in violation of a seven-week-old truce on Monday, causing no casualties or damage, an Israeli army spokesman said.

He said the rocket hit an empty field outside the city of Sderot, which was hard-hit by Palestinian rocket and mortar fire before the truce between Israel and the Hamas rulers of Gaza went into effect on June 19.

In all 40 rockets and mortar rounds have been fired from Gaza since the start of the Egyptian-mediated truce, the spokesman said.

Hamas, an Islamist movement that seized power in Gaza in June 2007, insists it is respecting the truce and has vowed to crack down on smaller Palestinian militant movements which still fire at Israel.

On Sunday, Israeli Defence Minister Ehud Barak told local television that the truce was effectively halting what used to be an almost daily barrage of rockets.