Israeli warplanes have carried out at least 13 air strikes on the Gaza Strip, according to Palestinian sources and witnesses.
There are reports of some injuries - three children are said to have been slightly injured by flying debris - but none of deaths.
Four strikes took place near the town of Khan Younis, where two Israeli soldiers died in clashes with Palestinian fighters last week, the BBC reports.
Buildings belonging to the Islamist organisation Hamas, which controls Gaza, were hit. Reuters news agency quotes an Israeli military spokesman confirming attacks that targeted two weapons-manufacturing plants and two arms caches.
Leaflet drop denied
Palestinian news agencies say Israeli aircraft dropped leaflets over parts of Gaza on Thursday warning residents of retaliation for the killing of the soldiers, for which Hamas's military wing has claimed responsibility.
A professor of political science at Al Azhar University in Gaza City, Mkhmaimar Abu-Sada, who lives very close to where the explosions occurred, says residents were told the Israelis were getting ready to launch some kind of attack.
Israel denies, however, that leaflets were dropped, saying it doesn't give warnings of such attacks.
A BBC correspondent says the strikes are the most serious for more than a year.