Israeli aircraft bombed a building in the Hamas-ruled Gaza Strip on Sunday which the military said had been used by Palestinians to access a tunnel intended for cross-border attacks in Israel, Reuters reported.
The air strike, in which no one was hurt, took place in the early hours shortly after Hamas said unidentified Palestinians had set off explosive devices at two of its security compounds in Gaza City.
With an Egyptian-mediated truce mostly holding since its war with Israel early this year, Hamas has cracked down on perceived internal threats from the rival secular Fatah faction and breakaway Islamists aligned with al Qaeda.
Hamas described the target of the Israeli air strike as "open ground" but witnesses said it was a building with two rooms and a courtyard, which were ravaged by the attack.
The Israeli military said in a statement its air force carried out the strike in response to a rocket fired from Gaza into Israel on Saturday, which caused no damage. There was no claim of responsibility for the rocket attack from any Palestinian faction.
"The tunnel was intended to be used for an infiltration into Israeli territory in order to execute a terrorist attack," the statement said. "It was dug from underneath a building located 1.5 kilometers away from the security fence."
An Israeli security source said intelligence indicated the tunnel had been dug by several Palestinian factions other than Hamas.
Hamas shuns the Jewish state but has signaled a willingness to enter into a long-term truce. Egypt and Germany are trying to broker the release by the Islamist group of Gilad Shalit, an Israeli soldier abducted in a cross-border tunnel raid in June 2006, in exchange for freeing hundreds of Palestinians held in Israeli jails.
Earlier on Sunday, Hamas said unidentified individuals set off bombs at its Ansar-2 jail and the Gaza residence of Palestinian President Mahmoud Abbas, who has stayed away from the territory since his Fatah faction was forced out by Hamas in a 2007 civil war.
No one was hurt in the blasts, which residents described as sounding like hand-laid bombs or grenades. Israeli military sources denied involvement.
Hamas crushed Fatah in a 2006 vote only to find itself isolated by the West for refusing to make peace with Israel.
With Gaza sinking into poverty and disarray, the group is wary of domestic challengers. An al Qaeda-linked faction's August 14 declaration of secession in southern Gaza led to a Hamas police onslaught in which 28 people were killed.