Two Palestinians were shot dead by Border Police at a Nakba protest outside the Ofer Military Prison near Ramallah, Palestinian sources reported Thursday.

Hospital officials said Muhammad Abu Thahr, 15, and Nadim Nuwara, 17, were both shot in the chest outside Israel's Ofer Prison near the Palestinian city of Ramallah in the occupied West Bank. According to the sources, they were shot with live ammunition.

Three youths were hospitalized with bullet wounds, medical sources in Ramallah reported. One had a chest wound and was operated on immediately. The other two were wounded in their limbs.

The Israeli military said that rubber bullets, stun grenades and tear gas – but not live ammunition - were used at the site of the incident. The Israel Defense Forces has launched an investigation.

Thousands of Palestinians marked Nakba Day on Thursday with rallies throughout the West Bank cities of Ramallah, Nablus, Bethlehem and Hebron.

Clashes between Palestinians and Israeli security forces were reported in Ramallah and Hebron, where 11 people were reported injured by rubber bullets and smoke inhalation.

Four Palestinians were detained on suspicion of throwing stones at a 200-strong protest in Damascus Gate in Jerusalem's Old City.

Nakba is the Palestinian term for the “catastrophe” they suffered upon Israel’s establishment on May 14, 1948, which led to the displacement of around 700,000 Palestinians, which today number 5 million refugees, as registered by UNRWA.

A 66-second siren marking 66 years since the Nakba sounded in Ramallah, where Palestinians marched from the tomb of Yasser Arafat to Al Manara Square in the city's downtown district.

Palestinian security sources told Haaretz that the leadership would be examining the continuation of security coordination with Israel in the light of Thursday's events, including the use of live ammunition against non-violent protestors.

General Adnan Admiri, spokesman for the Palestinian security apparatus, attributed the violence to Israel's desire for revenge following the reconciliation between the Fatah and Hamas Palestinian factions.

"Israel wants to destroy any prospect of Palestinian unity," Admiri told Haaretz. "The shots fired at the youths represented the mercy killing of the peace process.

The Israeli government serves the radical right and has no positive view regarding the Palestinians. As a result, the Palestinian leadership is looking at all its options, including the future of security cooperation and the possibility of turning to the international community."