Jerusalem (AFP) - The Israeli military said Tuesday it did not know a weekend air strike on the Gaza border that killed three teens was targeting minors, after accusations of excessive force.

In a statement the military said the three Palestinians, aged 13 and 14 according to the Gaza health ministry, were believed to be planting a bomb by the border fence after dark on Sunday.

"Troops spotted a squad of three suspects approaching the border under the cover of darkness, in a crouched and suspicious manner," it said, adding that they were seen "sabotaging the fence and digging".

"The three operated in a way that was identical to previous incidents in which terror operatives had placed explosive devices in the same location."

The army said that before the strike was called in "warning shots were fired towards them, which they failed to heed" and that military spotters "did not positively identify that they were minors".

The incident occurred with tensions high along the border after months of protests and clashes.

The boys were identified by the Gaza health ministry as Khaled abu Said, 14, Mohammed Abu Zaher and Mohammed al-Satari, both 13.

They came from the village of Wadi al-Salqa around a kilometre from the border fence.

The Gaza-based Palestinian Centre for Human Rights accused the Israeli's of an "excessive use of force" and said investigations concluded the three entered the area "in an attempt to sneak through the border fence".

It said paramedics who retrieved the bodies on the Gazan side of the fence confirmed that the children did not have weapons.

It gave their ages as 14 and 15.

At least 218 Palestinians have been killed by Israeli fire in the demonstrations and clashes along the border since late March.

One Israeli soldier has been killed along the border since the protests began on March 30.

Israel says its actions are necessary to defend the border and stop infiltrations and attacks, which it accuses Hamas of seeking to orchestrate.

Palestinians and rights groups say protesters have been shot while posing little threat.

Israel and Palestinian militants in Gaza have fought three wars since 2008 and the recent unrest has sparked fears of a fourth.