DAMASCUS: At least 52 people died in clashes and bombings across Syria on Thursday, with activists calling for another day of protests as the uprising against President Bashar al-Assad enters its 16th month.

Fourteen people were also wounded when a suicide bomber blew up a vehicle near an important Shia shrine in the capital.

Another car bomb in the northwestern city of Idlib killed and wounded a number of soldiers, the Syrian Observatory for Human Rights said.

Secretary of State Hillary Clinton said meanwhile that the United States had held “constructive” talks with Russia but urged more action after days of feuding over the bloodshed in Syria.

Clinton, who on Tuesday accused Russia of fueling the violence by sending attack helicopters to Syria, said that Deputy Secretary of State Bill Burns met Russia's foreign minister on the sidelines of a conference in Afghanistan.

“My deputy Bill Burns had a constructive meeting in Kabul with Russian Foreign Minister (Sergei) Lavrov. We don't see eye to eye on all of the issues, but our discussions continue,” Clinton told a news conference.

Clinton said that US President Barack Obama would meet Russian President Vladimir Putin at next week's Group of 20 summit in Los Cabos, Mexico.

Monitors say more than 14,100 people, mostly civilians; have died since a peaceful uprising erupted on March 15, 2011, prompting a bloody crackdown by Assad's forces that eventually prompted an armed reaction.

More than 2,302 have reportedly died in the past month alone.

Official news agency SANA said that in Damascus a vehicle exploded in a garage 50 metres (yards) from the Shia shrine and caused substantial damage, with the “terrorist” who launched the operation killed.

The Observatory, citing anti-regime activists, said it went off near security offices, damaging the apparent target as well as the shrine, as seen in a video posted on the Internet.

Most of Syria's 22-million populations are Sunni, while its minorities include Alawites, an offshoot Shia community to which Assad belongs.

As the death toll soars, Amnesty International accused the Syrian regime of committing crimes against humanity to punish communities supporting rebels.

The London-based group called for an international response after saying it had fresh evidence that victims, including children, had been dragged from their homes and shot dead by soldiers, who in some cases then set the bodies on fire.

As on nearly every Friday since the uprising began, activists have called for nationwide demonstrations after weekly prayers, with this week's slogan being “Always prepared for a strong mobilisation.”

Around the country, the Observatory said at least 33 civilians, 13 soldiers and six rebels died in combat between troops and insurgents and as the army shelled a number of rebel-held towns.

Areas in the provinces of Homs, Daraa, Damascus, Aleppo, Deir Ezzor and Idlib were all targeted, the London-based Observatory said.

- 'Strong stench of dead bodies –

Meanwhile, UN observers visited Al-Haffe town in the Mediterranean province of Latakia, a day after Syrian authorities said the area had been “cleansed” of rebel fighters, a UN spokeswoman in Damascus said.

On Wednesday, rebels withdrew from the besieged town and nearby villages that had been under intense regime shelling for eight days, the Observatory said.

The UN Supervisory Mission in Syria (UNSMIS) said the observers reported finding it all but deserted with a strong stench of dead bodies and most state buildings gutted.

State television said the observers had “inspected the vandalism and destruction wrought by the terrorists.”

The United Nations and opposition activists had expressed fears of a massacre if pro-government forces entered the town, just 16 kilometres (10 miles) from Assad's mainly Alawite hometown of Qardaha.

Opposition sources said anti-Assad groups are to meet in Istanbul on Friday and Saturday in a bid to settle their differences and close ranks.

Senior members of the main opposition Syrian National Council, the Kurdish National Council and smaller groups are to take part, they said.

“It is kind of a last call to join us,” an SNC source said on condition of anonymity.

On the diplomatic front, British Foreign Minister William Hague urged Russia and Iran to use their “full influence” over ally Syria to achieve a peaceful end to the bloody uprising.

China, meanwhile, said it disapproved of “one-sided” sanctions and pressure on Syria after France raised the prospect of a new raft of punitive measures against Assad's regime.