By Rachel Harvey BBC correspondent in Gaza City

The Palestinian militant organisation Hamas has called on children to refrain from futile attacks against Israelis.

Too many young lives lost at the fences of Israeli settlements would be a catastrophe for the future of the Palestinian struggle

Hamas statement

In an official statement, the organisation said that too many precious young lives were being lost.

Overnight, three teenage Palestinian boys were shot dead by Israeli security forces as they were trying to break into an Israeli settlement in the Gaza Strip.

The Hamas statement calls on Palestinian children to remember that their lives are precious, and should not be sacrificed.

"Too many young lives lost at the fences of Israeli settlements would be a catastrophe for the future of the Palestinian struggle," the statement said.

Children should be taught their lives are precious, Hamas says

Hamas is calling on teachers and religious leaders to spread the message of restraint among young Palestinians.

The move comes after a number of recent unsuccessful attempts by Palestinian boys to infiltrate Israeli settlements.

In the most recent incident on Tuesday night, three teenagers were shot dead by Israeli security forces as they tried to break into the Netzarim settlement in the centre of the Gaza Strip.

In a separate development, three people have been killed in an explosion near the Jabaliya refugee camp in the north of Gaza.

The circumstances of the blast are not clear, but eyewitnesses say four houses have been damaged.

Tension remains high, with speculation growing about what the next phase of Israel's campaign against militant activity might be.

The Israeli Prime Minister Ariel Sharon said on Tuesday that he had not ruled out further operations in Gaza if it became necessary.