A hardline Islamist group claimed a rocket attack against southern Israel on Thursday, in a statement that condemned a historic visit by US President Barack Obama to the region.
In a statement headlined "The demolition of Sderot by rocket bombardment in reaction to the visit of the dog Obama," the Salafist Aknaf Bayt al-Maqdis group said it was responsible for an attack launched from Gaza.
Two rockets hit southern Israel, one landing in the town of Sderot on Thursday morning before Obama travelled from Jerusalem to the West Bank city of Ramallah to hold talks with president Mahmud Abbas, leader of the Palestinian Authority.
The United Nations condemned the attacks and called for restraint.
"We condemn all rocket fire and call for it to stop," a UN statement said. "We urge restraint and we remind all sides of their obligations under international humanitarian law to protect civilians."
Israel retaliated to the fire by cutting the distance from the shore that Gaza fishermen are allowed to sail from six to three miles and shutting the Kerem Shalom goods crossing from Israel into the territory, a military statement said.
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It added that the sanctions would remain in place until the military received fresh instructions from the government.
Aknaf Bayt al-Maqdis (The Guardians of Jerusalem) "declares its responsibility for the rockets fired towards the Zionist violator Sderot this morning March 21, 2013," the statement said.
The military nevertheless said it considered the militant Islamic Hamas, which governs the Gaza Strip, to be responsible.
"The Israel Defence Forces consider this incident with great severity and holds the Hamas terror organisation responsible for any hostile activity emanating from the Gaza Strip," the statement said.
But the Islamist Hamas implicitly denied the charge.
Spokesman Sami Abu Zuhri told AFP Hamas "considers talk of rocket fire to be merely Israeli accusations aimed at gaining sympathy from Obama... and inciting him against Palestinians."
Hamas's relations with hardline groups in Gaza have sharply deteriorated since the movement violently cracked down on Salafist radicals in 2009.