Syrian security forces on Sunday killed at least 20 people across the country and flooded a tense neighborhood where a mourner was shot dead in the largest anti-regime rally seen in Damascus, activists said.

Regime troops killed nine people in the restive northwestern province of Idlib, nine in the central protest hub of Homs, one in the eastern province of Deir al-Zour and another in the southern province of Daraa, the cradle of the uprising, the Local Coordination Committees, the main activist group spurring protests on the ground, said.

The top U.S. military commander said Sunday he believed it would be "premature" to take military action against Iran in response to its nuclear program, as Britain urged Israel to give the diplomatic route a chance to succeed.

U.S. General Martin Dempsey, chairman of the Joint Chiefs of Staff, told CNN's "Fareed Zakaria GPS" program that economic sanctions have to be given a chance to work, and the United States and its allies should be better prepared for a military option.

The president of the United Arab Emirates has issued a decree granting citizenship to more than 1,000 children of Emirati women married to foreigners, the official WAM news agency reported on Sunday.

"President Sheikh Khalifa bin Zayed al-Nahayan has issued decrees granting citizenship to 1,117 children of UAE women married to foreigners who satisfied requirements for citizenship," WAM reported.

A roadside bomb blast killed four people and injured 10 other passengers on a bus east of the Algerian capital on Sunday, local news websites reported.

A security source confirmed the blast to AFP but did not give a toll or say whether the victims were civilians or military.

Egypt decided on Sunday to recall its ambassador to Syria, the Foreign Ministry announced, as Arab states pile pressure on Damascus over its crackdown on dissent that has left thousands dead.

Foreign Minister Mohammed Amr recalled the Egyptian ambassador to Damascus "and it was decided that the ambassador will remain in Cairo until further notice," ministry spokesman Amr Rushdi said in a statement.

Israeli police said they arrested three Palestinians in the grounds of the flashpoint al-Aqsa mosque complex in Jerusalem on Sunday after tourists visiting the site as well as police were stoned.

"Stones were thrown at tourists and police officers, police have made three arrests ... three suspects involved in throwing stones," police spokesman Micky Rosenfeld told Agence France Presse. "The situation is calm at present," he said.

Gunmen assassinated a senior prosecutor and a judge in a restive province in northwest Syria on Sunday, the country's state news agency said, while activists reported that security forces shelled rebel-held areas in the besieged city of Homs.

SANA news agency said gunmen opened fire in the morning on a car carrying Idlib provincial state prosecutor Nidal Ghazal and judge Mohammed Ziadeh.

The Syrian army has been laying siege to the ancient city of Palmyra, a world heritage site, since early February and shooting at anything that moves from a historic citadel, residents say.

"Palmyra is surrounded by the army from all fronts: the Arab citadel, the olive and palm tree groves, the desert, the city," one resident told AFP by telephone, adding that the operation began on February 4.

A suicide bomber blew himself up in front of a Baghdad police academy Sunday, killing 15 people and wounding more than 20 others in the deadliest attack for weeks in the Iraqi capital, security officials said.

At least seven other people were killed in attacks elsewhere in Iraq.

U.S. Deputy National Security Advisor John Brennan met with Yemen's vice president on Saturday and expressed Washington's commitment to provide support to the troubled country, official reports said.

"The U.S. will stand side by side with Yemen as it works to emerge from these difficult circumstances," the official SABA news agency quoted Brennan as saying in a meeting with Abdrabuh Mansur Hadi in Sanaa.