Israeli troops open fire at a crowd waiting to meet the freed Palestinian prisoners.
At least two people are dead and three injured after a blast outside a Hamas base.
“We are not aware of this incident,” the spokeswoman said.
Israel regularly launches attacks against Palestinian fighters in the Gaza Strip in an attempt to stop rockets being fired into nearby towns, but tensions between Hamas and the rival Fatah faction have also been running high in recent months.
Hamas seized full control of the territory after heavy fighting with security forces loyal to Mahmoud Abbas, the Palestinian president, in June.