Two Palestinian suicide bombers blew themselves up in the closely guarded Israeli seaport of Ashdod on Sunday, killing nine Israelis and wounding 18, according to police.
Two Palestinian militant groups, Hamas and Al Aqsa Martyrs'' Brigades, claimed joint responsibility.
The assailants came from the Jebaliya refugee camp in the Gaza Strip, and were sent to avenge the killings of militants in recent Israeli army raids, the statements said.
It was the first attack of its kind in more than three years of Israeli-Palestinian fighting, and underscored Israel''s vulnerability, despite stringent security measures.
In 111 bombings since 2000, attackers had generally targeted buses, cafes and shopping malls.
Sunday''s explosions went off just before 5 p.m. (1500 GMT) in two separate areas of the port.
Police initially believed that the explosions were set off accidentally.
However, officers said they became suspicious when they saw the bodies of the two apparent bombers.
Police and rescue services rushed to the scene and closed off the area.
It was the first attack of its kind at an Israeli seaport during more than three years of Israeli-Palestinian violence.
A member of the Al Aqsa brigades, an armed group with ties to Palestinian leader Yasser Arafat''s Fatah movement, identified the assailants as Nabil Massoud and Mohammed Salem from the Jebaliya refugee camp.
Ashdod is on the Mediterranean coast in the southern part of Israel, not far from the Gaza Strip.
It was not immediately clear how the assailants were able to get into Israel. The Gaza Strip is ringed by tall fences, and labourers crossing into Israel have to undergo stringent security checks.