A double suicide bombing in the southern Israeli port area of Ashdod has killed at least 11 people.
The explosions went off near warehouses
The blasts went off just before 1700 (1500 GMT) on Sunday in two separate areas of the busy port, witnesses say.
A summit between the Palestinian and Israeli leaders has been postponed indefinitely after the attacks.
Explosions were heard in Gaza City hours after the bombings, with Palestinian witnesses saying they were caused by an Israeli air strike.
Residents told the Associated Press news agency that two workshops were hit in the strikes; it is not yet clear if there have been casualties.
The al-Aqsa Martyrs' Brigades said it carried out the Ashdod attack, in co-operation with the largest Palestinian militant organisation, Hamas.
It is reportedly the first deadly attack on a strategic installation in at least three years of Israeli-Palestinian conflict.
A Palestinian militant had entered the port and asked for water - and the moment he was shown where there was a tap "he blew up", an employee of the port quoted one of his injured colleagues as saying.
It is unclear how the bombers managed to enter the area
Police initially thought that the explosions were set off accidentally.
However, officers said they became suspicious after seeing the bodies of the two apparent bombers.
An al-Aqsa source has named the bombers as al-Aqsa
member Nabil Massud, 18, and Mohammed Salem, also 18, from Hamas' armed wing, the Ezzedine al-Qassam Brigades.
Both were reportedly from the Jabaliya refugee camp in the northern Gaza Strip.
A second al-Aqsa source told the French news agency AFP that the attack was revenge for the killing of five al-Aqsa members in Jenin on Wednesday.
BBC correspondent Matthew Price in Jerusalem says the fact that both bombers came from the Gaza Strip will be worrying to Israeli security forces, who thought they had made it almost impossible for militants to get out of Gaza.
Ashdod is a busy port on the Mediterranean coast, close to the Gaza Strip.
"A port, by nature, is a very busy place... there are many people coming and going. It is impossible to seal the entire country hermetically," Israeli Cabinet Minister Yosef Paritzky said.
He said the militants had "found a weak point and exploited it".
The assailants might have intended to detonate themselves near chemical storage tanks in the port, one police officer said.
It is unclear how the bombers entered the area as the Gaza Strip is encircled by tall
fences, and entrants have to undergo
stringent security checks.