Two car bombs struck Shiite pilgrims Monday in an Iraqi holy city, killing at least 18 people as crowds massed for religious rituals marking the end of a 40-day mourning period for the Islamic sect's most beloved saint.

The blasts in Karbala were the latest in nearly a week of attacks that have killed at least 159 people. The uptick in violence has shattered a lengthy period of calm and raised anew concerns about the readiness of Iraqi forces to take over their own security ahead of a full withdrawal by the U.S. military.

Egyptian Interior Minister Habib al-Adly said on Sunday that a Palestinian group was behind the New Year's church attack in the Mediterranean city of Alexandria that killed more than 20 people.

"The Palestinian Islamic Army, which has links to Al-Qaida, is behind the attack on the al-Qiddissin church in Alexandria," Adly said in a speech to mark Police Day, carried live on state television.

Car bombs killed six people and wounded 30 in and around Baghdad on Sunday, an Iraqi interior ministry official said.

The attacks came after a spate of violence across Iraq last week killed 116 people, breaking a relative calm that had settled after the formation of a new government a month ago.

Some 1,000 demonstrators from rural central Tunisia, calling for the resignation of the transitional government, reached the capital on Sunday.

The marchers, from a poor farming region where an uprising against authoritarian rule began last month, called for the resignation of a government put in place after the ouster of president Zine El Abidine Ben Ali.

Radical Shiite cleric Moqtada al-Sadr has returned to Iran after having only arrived in Iraq around two weeks ago, two senior officials within his movement said Saturday.

"He left Iraq on Thursday to go back to Iran," an aide to the firebrand cleric told Agence France Presse. "That's all we can tell you."

The pre-eminent institute of Islamic learning in the Sunni Muslim world said Thursday it is freezing its dialogue with the Vatican to protest Pope Benedict XVI's recent remarks calling for the protection of Christians in Egypt.

The move from Cairo's Al-Azhar comes as Muslim-Christian tensions have been rising in Egypt following the New Year's bombing on a Coptic Christian church in Alexandria that killed 21 people. Egypt's government has rejected international expressions of concern over the country's Christian minority as foreign meddling in its internal affairs.

Angry Palestinians mobbed French Foreign Minister Michele Alliot-Marie on Friday as she visited Gaza due to a "war crimes" remark wrongly attributed to her by Israeli radio.

The foreign minister, on her first visit to the enclave since taking over the post in November, was met by angry protesters as her convoy arrived, then again as she visited a hospital in Gaza City.

Senior White House adviser Dennis Ross and another top U.S. official arrived in Israel on Thursday for talks about Israel's "security needs," an official statement said.

Ross and David Hale, adviser to U.S. Middle East envoy George Mitchell, would "hold talks about questions regarding Israel's security needs as well as other issues related to regional security," Israeli Prime Minister Benjamin Netanyahu's office said.

At least 50 people died in a spate of explosions across Iraq on Thursday, including 45 in twin suicide car bombs that rocked the holy city of Karbala, the third major attack in as many days.

The attacks mostly targeted pilgrims marking the Shiite Muslim mourning day of Arbaeen, and were the latest in a series of bombings that have shattered a relative calm in Iraq following the formation of a new government last month.

A total of 13 civilians including children and women were killed Wednesday by a Taliban-style roadside bomb in eastern Afghanistan, officials in Kabul said.

The blast hit a three-wheeled vehicle and killed "13 of our innocent civilian compatriots, including women, children and elderly men," the interior ministry said in a statement.