Authorities in the Hamas-run Gaza Strip on Thursday executed two Palestinians for allegedly collaborating with Israel, the territory's interior ministry said.

"Two collaborators with the Israeli occupation, condemned to death for having given information leading to the martyrdom of two citizens, have been executed," a spokesman told Agence France Presse.

U.S. National Security Adviser Susan Rice met Israeli leaders Wednesday after the collapse of U.S.-brokered Middle East peace talks and amid allegations Israel was spying on its principal ally.

Rice started her visit by meeting Prime Minister Benjamin Netanyahu.

Israel plans to use detention without trial against Jewish extremists suspected of anti-Arab hate crimes, a minister said on Wednesday, as its failure to secure prosecutions drew mounting criticism.

As police confirmed yet another incident of nationalist-inspired vandalism, in which "Death to Arabs" and other racist graffiti was found in northern Israel, senior law enforcement officials were to discuss with ministers how to halt the wave of so-called "price tag" attacks.

Israel has called off an inquiry into alleged sex offenses by Energy Minister Silvan Shalom, an expected candidate for the presidency, the justice ministry announced Wednesday.

Attorney general Yehuda Weinstein said Shalom was immune from prosecution under Israel's statute of limitations, since an alleged incident dated back more than 10 years, the ministry said.

Unprecedented pressure on Hamas, from both Israel's blockade of Gaza and a hostile Egypt, forced the Islamist movement to accept reconciliation terms dictated by Palestinian President Mahmud Abbas, analysts say.

But Hamas's subservience to the Palestine Liberation Organization (PLO) in the context of the unity deal could work to its advantage, allowing it to return to its militant roots, freed from the responsibilities of governance.

Israel spies on the United States more than any other ally does and these activities have reached an alarming level, Newsweek magazine reported Tuesday.

The main targets are U.S. industrial and technical secrets, the weekly said, quoting classified briefings on legislation that would make it easier for Israeli citizens to get visas to enter America.

Israeli Foreign Minister Avigdor Lieberman on Wednesday denounced as a "fifth column" thousands of Arab Israelis who joined a demonstration calling for the right of return for Palestinian refugees.

Around 10,000 protesters, many waving Palestinian flags, joined a rally in northern Israel on Tuesday to remember 530 villages from which some 760,000 people fled or were expelled following the creation of the Jewish state in 1948.

Egypt's former army chief and leading presidential candidate Abdel Fattah al-Sisi suggested on Tuesday he would not receive an Israeli prime minister if the Jewish state does not make concessions to Palestinians in peace talks.

The retired field marshal, who toppled elected Islamist president Mohamed Morsi in July, is expected to sweep the May 26-27 election. His only rival is leftist politician Hamdeen Sabbahi.

Graffiti was found Tuesday on a rabbi's tomb in northern Israel in what appeared to be an act of revenge following a recent string of similar attacks targeting Arabs.

A swastika was painted on the tomb near the town of Karmiel, along with the words: "The price to be paid... will be paid," police spokeswoman Louba Samri told Agence France Presse.

Israeli President Shimon Peres said Tuesday that Prime Minister Benjamin Netanyahu blocked a 2011 peace agreement he had secretly negotiated with Palestinian leader Mahmoud Abbas.

Peres said he and Abbas had finalized a draft agreement in a series of secret meetings in neighboring Jordan but the draft was rejected by Netanyahu's right-leaning government.