A small Israeli force has entered the Gaza Strip, but the army offered no details beyond confirming the operation was taking place.
Local Palestinian residents said the Israeli force included tanks and other armoured vehicles.
Tensions have risen sharply between Israel and the Islamist group Hamas, which took undisputed control of Gaza in May after routing pro-Fatah rivals.
There were no immediate reports of injuries or damage.
A spokesman confirmed military activity in the area by a small force against what he called "terror threats".
Troops entered the coastal strip at the southern Sufa crossing.
Palestinian sources quoted by the Israeli media said clashes broke out between gunmen and Israeli troops, with the help of helicopters and tanks.
On Thursday night, Israeli forces accompanied by helicopters were reported to be operating in the central and northern Gaza Strip.
Daily violence between militants in Gaza and Israeli troops - with rocket attacks on one side and incursions and air strikes on the other - has led to speculation that Israel may launch a large-scale invasion.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~56~RS~)