Exchange of fire between Gaza and Israel
Palestinian militants in Gaza have fired a missile across the border into Israel for the second time in two days.
Hours earlier the Israeli military carried out air strikes in Gaza.
This was the first such strike since a ceasefire ended the short war between Israel and Hamas in November last year.
There were no injuries from the Israeli strike nor the Palestinian rocket fire, but Israeli defence Minister Moshe Yaalon said Israel would not allow such firing to become routine.
Overnight Israeli planes bombed open land in Northern Gaza. Israel said it was responding to Palestinian rocket fire on Tuesday.
Palestinian militants fired a second rocket on Wednesday morning.
Sirens sounded in the Israeli town of Sderot warning of incoming rockets and forcing residents to take cover.
A BBC correspondent in Gaza, Jon Donnison, says neither Israel nor Hamas are thought to want another escalation in violence but it is a reminder the ceasefire is fragile and that the underlying conflict remains.
Some will fear this could be the start of a familiar cycle of retaliatory attacks from both sides, our correspondent adds.
More than 160 Palestinians and 6 Israelis were killed in 8 days of fighting last November.
The United Nations says four Palestinians have been killed by Israeli military action in Gaza since the ceasefire was declared.