An Israeli soldier and a Palestinian have been killed during an exchange of fire along the Gaza border.
The Israeli army said that the Palestinian cut through the border fence and opened fire on Israeli troops, who then shot back.
Separately, an Israeli air strike targeted militants travelling on a motorbike, sources in Gaza say. There are reports of serious injuries.
The incidents come after several months of relative calm along the Gaza border.
There are reports that there was heavy mist in the area making it easier to approach the fence undetected early on Friday.
According to Israeli media, the exchange of fire happened near the Kissufim crossing.
It is not uncommon for the Israeli army to open fire on Palestinians who approach the fence.
But it is rare for a Palestinian to break through and for an Israeli soldier to be killed in such an exchange, the BBC's Jon Donnison reports.
Residents of southern Israel, quoted by the Associated Press, said they heard gunfire in the early morning and heard Israeli helicopters circling in the air.
They also said tank shells were fired into Gaza that set fire to fields.
Just hours later, sources in Gaza reported the Israeli air strike on suspected militants.
Israel has not commented on this, and it was not immediately clear if the firefight and the air strike were connected.
The Israeli military maintains an exclusion zone on the Gaza side of the boundary between Gaza and Israel, and troops regularly carry out military activity in the area and fire on Palestinians who approach the fence.