By Ori Lewis

JERUSALEM (Reuters) - Two Israeli security guards will not face charges for shooting dead a Palestinian woman brandishing a knife and her brother, the Justice Ministry said on Wednesday.

Prosecutors determined that the two guards, whose names have been withheld, acted lawfully in the face of what they considered a threat. Israeli police said after the attack in April the Palestinian siblings had both had knives and tried to carry out an attack at Qalandia checkpoint in the West Bank.

"After examining the evidence, including the security guards' versions and the video footage ... the case has been closed against one of the guards for lack of evidence and the other because he was blameless," the ministry statement said.

Camera footage, the statement said, showed 16-year-old Ibrahim Taha with one hand in his pocket while trying to pull his sister, Maram Abu Ismail, 23, away from guards.

But it said neither had heeded calls to back away and that a subsequent search of Ibrahim's body uncovered several knives, including one identical to the one brandished and then hurled at a guard by his sister.

Owing to the swift pace of events and security concerns during a period of frequent Palestinian attacks, the self-defense argument of the guard who shot Taha "cannot be ruled out", the statement said.

Palestinian authorities said at the time of the incident that the siblings had been en route to Jerusalem for a medical appointment and had accidentally entered a vehicles-only lane on foot.

Over the past year, Palestinians, many acting alone and often using rudimentary weapons, have killed at least 35 Israelis and two visiting Americans in similar attacks.

During the same period, at least 223 Palestinians have died in violent incidents in the occupied West Bank, East Jerusalem and the Gaza Strip. Of those, Israel has identified 151 as assailants, while others were killed during clashes and protests.

Palestinians have accused Israeli police and soldiers of using excessive force against many of the attackers.

In a separate case, an Israeli conscript is standing trial for manslaughter after he shot a Palestinian assailant who was lying on the ground after being seriously wounded by gunshots. If convicted, he could face up to 20 years in prison.

Palestinian leaders say assailants are acting out of desperation over the collapse in 2014 of peace talks and the expansion of Israeli settlements on occupied land that Palestinians seek for an independent state.

Some relatives of Palestinians killed while carrying out assaults say their actions were caused by personal problems or emotional distress.

(Writing by Ori Lewis; editing by Jeffrey Heller and Andrew Roche)