The shootings on Friday coincided with an invasion of the West Bank town of Bethlehem by Israeli troops.
The identities were not given and the circumstances surrounding their deaths were not immediately clear.
Palestinian sources however said the shootings took place near the settlement of Dugit, close to Beit Lahya.
The deaths brought to 3,730 the number of people killed since the start of the Palestinian intifada or uprising at the end of September 2000, including 2,788 Palestinians and 875 Israelis.
In invading Bethlehem, Israeli soldiers moved in on armoured vehicles from several directions, including the neighbouring towns of al-Khader, Jabaliya, Bait Sahour and Tekoa.
Sources said some of the troops reached Manger Square, beside the reputed birthplace of Jesus, without encountering opposition.
Bethlehem is one of the few places in the occupied West Bank that the Israeli army had evacuated and handed over to the Palestinian Authority.
On Thursday morning a bomber from Bethlehem blew himself up in a bus in west Jerusalem near the Israeli prime minister's residence, killing 10 people and wounding dozens.
Ariel Sharon held talks overnight with Defence Minister Shaul Mofaz and army officials on how to respond to the attack, an Israeli military source said.
The human bombing came a day after Israeli troops had killed eight Palestinians during an invasion of the Gaza Strip.