A suicide car bomber struck Cairo police headquarters Friday, the first of four blasts in Egypt's capital that killed six people on the eve of the anniversary of the 2011 uprising.

The bombings, all targeting the police, came as street clashes between Islamist supporters of deposed president Mohammed Morsi and backers of the military killed eight people, a day before planned rallies to mark the revolt that drove Hosni Mubarak from power.

A U.S. official downplayed Thursday the discovery by Israel of an al-Qaida cell it said was plotting to bomb the American Embassy in Tel Aviv, describing the group's plans as "aspirational."

Israeli authorities said Wednesday three members of a militant cell run by al-Qaida in annexed east Jerusalem had been arrested for plotting a wave of attacks across the country.

U.S. government officials saw as early as November hundreds of images of alleged mass torture and killings of detainees held by the Syrian regime, the State Department said Thursday.

But President Barack Obama's administration at the time decided against making public a report alleging the large-scale torture and murder of 11,000 detainees by Damascus, out of concern for the safety of the source and in order to identify the documents, deputy spokeswoman Marie Harf said.

U.S. Secretary of State John Kerry said Thursday that some countries might be prepared to send peacekeeping troops to Syria, as the U.N. leads efforts to bring the warring sides together and end the war.

The top U.S. diplomat also acknowledged in an interview with Dubai-based Al-Arabiya television that President Bashar Assad was not ready to make peace.

Syrian opposition chief Ahmed Jarba on Thursday announced that the regime has become a "political corpse," as U.N. mediator Lakhdar Brahimi met Syria's warring sides behind closed doors to lay the groundwork for direct talks after the first day of a peace conference ended in bitter exchanges.

"The world is now sure that Assad cannot stay and will not stay," Jarba said after meeting Brahimi.

Cyberactivists from the Arab world said Thursday they are facing "an unprecedented attack" from regimes in their countries, three years after the start of Internet-fueled uprisings in the region.

"Today there is an unprecedented attack against activists in general and cyberactivists in particular," said Hisham al-Miraat, advocacy director at the Global Voices, an international network of bloggers, translators and citizen journalists.

Egypt's prime minister said Thursday the spirit of the Arab Spring was still alive in his country and that the army chief likely to run for the presidency was no dictator, but more a De Gaulle figure.

"This was a great revolution," Hazem al-Beblawi said at a Davos World Economic Forum seminar.

Canada said on Thursday that it will provide around Can$100 million ($90 million, 65 million euros) to help Jordan cope with an influx of hundreds of thousands of Syrian refugees.

The pledge came as Canadian Prime Minister Stephen Harper held talks in Amman with Jordan's King Abdullah II about the Syrian conflict and its impact on the kingdom.

Syrian Kurds protested Thursday their exclusion from U.N.-brokered peace talks in Switzerland, and vowed to forge ahead with their own freedom drive in territories they control.

"Some forces are trying to exclude us from the solutions they are looking for, and they're not representing anybody," said Saleh Muslim, leader of the Kurdish Democratic Union Party (PYD).

Israeli Prime Minister Benjamin Netanyahu called on Europe on Thursday to demonstrate fairness in its Middle East policy, after a spat over settlements blew up last week.

Speaking to the World Economic Forum in Davos, Netanyahu said Europe could make a positive contribution in the Middle East but warned that it could also have a "negative effect."