The first attack on August 31 claimed the lives of four settlers, and the second on September 1 wounded two people east of Ramallah, the official said.
Hamas had claimed responsibility for gunning down four Israelis on the West Bank, and the September 1 attack came the day before the first direct Israeli-Palestinian talks for 20 months began in Washington.
Hamas later claimed to have made between 150 and 550 arrests over the killings but the Palestinian Authority said this was an exaggerated figure.
US President Barack Obama has branded the attack on two couples, including a pregnant woman, as "senseless slaughter," and warned about "extremists and rejectionists who, rather than seeking peace, are going to be seeking destruction.
"The message should go out to Hamas and everybody else who is taking credit for these heinous crimes that this is not going to stop us from not only ensuring a secure Israel, but also securing a longer-lasting peace in which people throughout the region can take a different course," he said.
Israeli Prime Minister Benjamin Netanyahu branded the killings "savagery and brutality."
Palestinian president Mahmud Abbas said the September attack in Kiryat Arba, a West Bank settlement, was intended to "disrupt the political process."
Hamas, which rules Gaza, is opposed to the peace talks and is a rival of Abbas's US-backed Palestinian Authority.
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Hamas had claimed responsibility for gunning down four Israelis on the West Bank, and the September 1 attack came the day before the first direct Israeli-Palestinian talks for 20 months began in Washington.
Hamas later claimed to have made between 150 and 550 arrests over the killings but the Palestinian Authority said this was an exaggerated figure.
US President Barack Obama has branded the attack on two couples, including a pregnant woman, as "senseless slaughter," and warned about "extremists and rejectionists who, rather than seeking peace, are going to be seeking destruction.
"The message should go out to Hamas and everybody else who is taking credit for these heinous crimes that this is not going to stop us from not only ensuring a secure Israel, but also securing a longer-lasting peace in which people throughout the region can take a different course," he said.
Israeli Prime Minister Benjamin Netanyahu branded the killings "savagery and brutality."
Palestinian president Mahmud Abbas said the September attack in Kiryat Arba, a West Bank settlement, was intended to "disrupt the political process."
Hamas, which rules Gaza, is opposed to the peace talks and is a rival of Abbas's US-backed Palestinian Authority.
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