Salafist politician Hazem Abu Ismail looks set to rejoin the presidential race after a court ruled on Wednesday that his mother was not a U.S. citizen, the official MENA news agency reported.

Under the country's electoral law, all candidates for the presidency, their parents and their wives must have only Egyptian citizenship.

NATO said Thursday it takes its responsibility to defend allies "extremely seriously" after member state Turkey said it may seek help after shootings along its border with Syria.

"We are deeply concerned by events in Syria, particularly the recent incidents on the border with our ally Turkey," NATO spokeswoman Carmen Romero told Agence France Presse.

British Prime Minister David Cameron urged Russia and China on Thursday to join the international community and help "tighten the noose" on the Syrian regime over its deadly crackdown on protests.

A U.N.-backed ceasefire to end 13 months of bloodshed in Syria appeared to be holding after coming into force at daybreak, but doubts remained about the compliance of President Bashar Assad's government with the peace plan.

China's foreign ministry on Thursday welcomed what it called the Syrian government's decision to uphold a "comprehensive ceasefire,” and urged it to fulfill its commitments.

"This will help ease the tense situation in Syria, and is an important step towards a political solution," said ministry spokesman Liu Weimin, after a U.N.-backed ceasefire to end 13 months of bloodshed in Syria came into force.

A ceasefire in Syria appeared to be holding on Thursday, as the Syrian government and its foes traded charges of trying to wreck U.N.-Arab League envoy Kofi Annan’s peace plan.

Renewed bloodshed on Thursday killed at least 23 people, putting to the test the hard-won ceasefire plan.

German Foreign Minister Guido Westerwelle Wednesday pressed Russia to distance itself from Syrian President Bashar al-Assad's deadly crackdown on opposition rebels.

"Russia has to make clear that it does not want to have anything to do with these acts of violence and this repression," Westerwelle said on the sidelines of a two-day meeting with Group of Eight ministers in Washington.

U.S. Secretary of State Hillary Clinton said Wednesday she is alarmed about the "ongoing violence" in Syria on the eve of a ceasefire deadline.

In remarks to the Group of Eight foreign ministers, she also voiced concern about the problems facing U.N.-Arab League envoy Kofi Annan as he tries to get Syria to implement his peace plan that calls for a ceasefire on Thursday.

Tunisian President Moncef Marzouki commemorated the 10th anniversary of a deadly attack on an ancient synagogue Wednesday, a move welcomed by the Arab nation's tiny Jewish population.

On April 11, 2002 the Tunisian Nizar Nawar carried out an al-Qaida-claimed suicide attack on the synagogue at Ghriba on the Mediterranean island of Djerba.

International envoy Kofi Annan said Wednesday he had received a written pledge from the Syrian regime to halt fighting from dawn on Thursday in line with his U.N. and Arab League-backed peace plan.

Annan had received a letter from Syria's foreign minister pledging "to cease all military fighting throughout Syrian territory as of 6:00 am tomorrow, while reserving the right to respond proportionately to any attacks carried out by armed terrorist groups against civilians, government forces or public and private property'," his spokesman said in a statement.

A Saudi court sentenced a radical cleric who fiercely supports the segregation of the sexes to five years in prison on Wednesday for "incitement" against the kingdom's rulers, media reported.

Youssef al-Ahmed was also sentenced to a five-year travel ban and fined 100,000 Saudi riyals ($26,600), said aleqt.com, the website of Al-Eqtesadiya daily.