Israeli naval gunboats opened fire off Gaza City's shore Tuesday, witnesses said.
The target of the attack, a day after Israel assassinated Hamas leader Ahmed Yassin in Gaza, was not immediately known.
Palestinian security sources said there were no reports of injuries and that two Israeli warships and two helicopters were in the area.
The Israeli army had no immediate comment.
CUETZALAN, Mexico (Reuters) - Six British armed forces cave explorers have been trapped underground for five days in central Mexico, but are not in imminent danger, the Ministry of Defence has said.
The six were trapped by an unexpected rainstorm during a combined services caving expedition last week in caverns near the coffee-growing town of Cuetzalan, 110 miles (175 km) northeast of Mexico City.
They had rejected help from Mexican rescuers and were waiting for the waters to recede. The incident was not made public until Tuesday.
"They are all experienced cavers and nobody is in imminent danger, they are all a bit bored but well," ministry spokeswoman Gemma Blackburn told Reuters in a telephone interview on Tuesday.
But she said specialist Navy cave divers were on their way from Britain in case they were needed to dive into the cavern to rescue the servicemen.
"Several inches of un-forecast rain fell, flooding a low-lying section of the cave. They are in an area that has never flooded, it is stocked with food, sleeping bags, a first aid kit and a cave radio," she said.
Mexican Civil Protection rescue workers said other British cavers were in touch with their trapped colleagues from the surface via radio telephone.
The trapped armed forces personnel were all members of the Combined Services Caving Association taking part in an exercise called Cuetzalan Tiger.
The network of underground galleries near Cuetzalan is one of the most extensive in Latin America. It was first explored in the 1970s by British cavers, who have surveyed more than 60 miles (100 km) of passageways to date.
A speleological Web site said the Cuetzalan region cave systems risked "serious threat" from flash floods.
Jose Ignacio Macias, spokesman for the Civil Protection Agency in Puebla state, where Cuetzalan is located, said strong currents underground were keeping the cavers from leaving.
Puebla state officials had said the cavers became trapped after part of the cave collapsed.