Leaders of Syria's largest opposition movement met behind closed doors in Tunisia on Saturday to discuss ways of accelerating the downfall of President Bashar Assad.

Tunisia is hosting a three-day meeting of Syrian opposition groups formed before and since the launch of the March uprising against Assad's regime.

Amnesty International and Human Rights Watch have urged Saudi Arabia to scrap amputation sentences against six men convicted of robbery, with HRW on Saturday calling the sentencing "prohibited torture."

"Cutting off someone's hands and feet is torture, plain and simple," said HRW senior Middle East researcher Christoph Wilcke.

Qatar branded as "regrettable" on Saturday an airport attack on Russia's ambassador last month, saying ties with Moscow were solid although Russia downgraded relations with the Gulf state.

"Our relations with Russia are solid, strong and important and this regrettable incident will not affect them," Prime Minister Sheikh Hamad bin Jassem al-Thani told reporters on the sidelines of an Arab League meeting on the Syria crisis.

A Yemeni military commission began returning the capital to normality Saturday, removing checkpoints and barricades erected during months of deadly protests against President Ali Abdullah Saleh.

Bulldozers were seen removing sand berms thrown up by the pro-Saleh Central Security service at the Asser roundabout, under the supervision of members of the joint commission formed by the new opposition-led government, an Agence France Presse correspondent reported.

Thousands of Tunisians rallied on Saturday to commemorate a young fruitseller's desperate gesture a year ago which unleashed the pioneering revolution of the Arab Spring.

Newly-elected President Moncef Marzouki joined the crowds in the town of Sidi Bouzid, where Mohamed Bouazizi's altercation with a policewoman and his subsequent self-immolation set off a wave of protests that toppled long-standing dictators and dramatically changed the Arab world.

The Arab League on Saturday threatened to take Syria to the U.N. over its deadly crackdown on dissent but an Iraqi mediator said he had "positive" talks in Syria aimed at defusing the nine-month crisis.

The Qatari prime minister warned that the Arab League would take Syria to the U.N. Security Council if it persisted in refusing to allow observers into the country to monitor the protection of civilians.

Egyptian Prime Minister Kamal al-Ganzuri on Saturday accused protesters who engaged in deadly clashes with security forces in Cairo a day earlier of being counter-revolutionaries.

"Those who are in Tahrir Square (epicenter of the revolution that overthrew President Hosni Mubarak in February) are not the youth of the revolution," Ganzuri told a press conference.

An Iraqi team held "positive" talks with Syrian President Bashar Assad on Saturday in a bid to end the deadlock over an Arab League plan to stop nine months of bloodshed, its leader told Agence France Presse.

"I am on my way to Cairo for a meeting with the Arab League after holding positive talks with President Assad," National Security Adviser Falah al-Fayadh said.

U.S. Defense Secretary Leon Panetta arrived in Tripoli Saturday on the first visit to Libya by a Pentagon chief to study up close the security needs of the new government.

During the visit, which will last only a few hours, Panetta will meet with Defense Minister Osama Jouili and Prime Minister Abdul Rahim al-Kib, said an AFP correspondent traveling with him.

Violence raged in the administrative heart of Egypt's capital on Saturday as troops and police deployed in force after clashes with protesters against continued military rule left nine people dead.

Smoke billowed over Tahrir Square, the iconic focus of the protest movement that overthrew veteran president Hosni Mubarak in February, after two nearby government offices caught fire, an Agence France Presse correspondent said.