Two Israeli tourists and their Egyptian guide were shot dead on Sunday in the Egyptian city of Alexandria, the Israeli foreign ministry said.
A policeman alleged to have carried out the shooting in the Sawari district of Alexandria was in custody, two Egyptian security sources said, speaking on condition of anonymity.
One Egyptian was injured in the shooting, the first such attack on Israelis in Egypt in decades. The Egyptian interior ministry did not respond to a request for comment.
The shooting happened one day after an attack against Israel by Islamist group Hamas, for which Israel vowed "mighty vengeance" in response. Hundreds of Palestinians and Israelis have been killed.
Policeman 'provoked'
According to one of the Egyptian sources, the policeman said he lost control and fired randomly on the tourist group after being provoked.
Egypt was the first Arab nation to normalize relations with Israel, but while the two countries cooperate closely on security and energy many Egyptians, like others across the Arab world, continue to sympathize with the Palestinian cause.
The head of Egyptian intelligence was in close contact with officials from Israel and Hamas following the outbreak of violence, three security sources said on Saturday.
In June, three Israeli soldiers and one Egyptian security officer were killed in an hours-long incident near the countries' border.