Mahmud Bassal, spokesman for the Gaza Strip's civil defence agency, told AFP that the Israeli strike "on a group of citizens in the Netzarim area in south Gaza City" resulted in "four martyrs including two brothers", all men in their 20s.

The Israeli military said that its air forces had struck "several terrorists engaged in suspicious activity posing a threat to IDF troops".

Later in a separate statement, the military said it targeted a militant in southern Gaza in another air strike.

"Earlier today, a terrorist was identified conducting surveillance activities and gathering intelligence on IDF soldiers in southern Gaza," the military statement said.

"The IAF (air force) conducted a strike on the terrorist to remove the threat," it added, not specifying whether the militant was killed.

Israel has carried out near-daily air strikes in Gaza since early March, often targeting what the military said were militants planting explosive devices.

A fragile truce in its war with Hamas, in effect since January 19, has largely held despite the attacks and with no agreement yet on extending the ceasefire.

The first phase of the truce ended in early March, but both Israel and Hamas have refrained from returning to all-out war.

Hamas has repeatedly called for implementing the second phase of the ceasefire, which should lead to a permanent end to the war, a full Israeli withdrawal from Gaza and the release of more hostages in return for Palestinian prisoners.

Israel says it prefers an extension of phase one of the ceasefire until mid-April.