Intensive clashes were taking place between the Syrian government troops and rebels in al-Abbasiyeen area in Damascus and sounds of explosions, shelling and gunshots were heard, Al Arabiya reported on Wednesday citing activists at the Local Coordination Committees (LCC), as Russia signaled it is prepared to see Syrian President Bashar al-Assad leave power as part of a political settlement.

Loud explosions were heard in al-Qaboun neighborhoods and in Baghdad Street. A number of explosions have also rocked the city of Lattakia, the Syrian Sham Network said, as at least 51 people were killed on Tuesday in the violent crackdown of the Syrian forces against dissents across the country.

The LCC said that the city of Zabadany was exposed to intensive shelling and the houses were targeted as mass protests went out overnight.

Heavy clashes were reported between the Free Syrian Army (FSA) and the troops loyal to Assad in Harasta on the outskirts of Damascus, as a number of protests kicked off from mosques in the town.

LCC activists told Al Arabiya that intensive shelling was reported in Hama and Deraa. Heavy clashes were also reported in the Kurds Mountain in Lattakia, they said.

Meanwhile, a senior Russian diplomat said on Tuesday that Russia is prepared to see President Assad leave power as part of a political settlement following 15 months of bloodshed, but is not in talks with other nations on the fate of the Syrian leader.

Deputy Foreign Minister Gennady Gatilov also said a Yemen-style power transition was unlikely to work in Syria because many of Assad’s foes are unwilling to negotiate with the government, Russian news agency Itar-Tass reported.

Moscow has used its U.N. Security Council veto and other tools to protect Assad, who has given Russia a firm Middle East foothold and is a client for Russian weapons.

Russia is under pressure to abandon its support or at least push Assad harder to adhere to a U.N.-backed ceasefire and a faltering peace plan brokered by envoy Kofi Annan.

Gatilov reiterated Russian statements -- also repeated on Friday by President Vladimir Putin -- that Moscow is open to Assad’s exit from power if it results from a Syrian political dialogue without foreign interference, according to Reuters.

“We have never said or posed the condition that Assad must necessarily stay in power as the result of this political process,” state-run Itar-Tass quoted Gatilov as saying in Geneva, a day after a meeting Annan. “This issue must be resolved by the Syrians themselves.”

He said Russia “is not holding any contacts or discussions with anyone about whether Assad should stay in power or go.”

Gatilov expressed doubt the formula used in Yemen could succeed in Syria.

“It would be good if there was ... political desire on both sides that would allow for progress toward a resolution, and in that case it would probably be appropriate to talk about the Yemen model,” he said. “But in Syria, we see no such desire on the opposition side.”

U.S. President Barack Obama told G8 nations including Russia last month that Assad must leave power and pointed to Yemen, where foreign states helped engineer a handover from longtime leader Ali Abdullah Saleh to an administration led by his vice president, as a model for a potential transition.

Media reports have suggested Washington is trying to enlist Russia's support for such a plan. In a telephone call on Saturday with Russian Foreign Minister Sergei Lavrov, U.S. Secretary of State Hillary Clinton conveyed a message that “we’ve got to start working together to help the Syrians with a serious political transition strategy.”

Russia expressed “serious concern" about that decision in a Foreign Ministry statement on Tuesday, saying it was aimed “to undermine international efforts to foster a shift from confrontation to a political process.”

In Beijing, Putin and Chinese President Hu Jintao urged the world not to abandon Annan’s plan, which calls for a “political process” but does includes no specific call for Assad to leave power.

Syrian rebels said on Monday they were no longer bound by a U.N.-backed truce because Assad had failed to observe their Friday deadline to implement the ceasefire.

Russia and China used their U.N. Security Council vetoes in February to block a Western-backed resolution supporting an Arab League call for Assad to cede power.

Syria, meanwhile, has agreed to allow humanitarian workers and supplies into four of its provinces hit hardest by violence, a promise of some relief in a nation where 1 million people need aid urgently due to the fighting, officials said Tuesday, The Associated Press reported.

At the same time, however, Damascus plunged itself into further international isolation by labeling U.S. and European envoys as unwelcome in retaliation for earlier Western expulsions of Syrian diplomats.

Syria’s uprising began in March 2011 with mostly peaceful protests, but a brutal government crackdown using tanks, machine guns and snipers led many in the opposition to take up arms. The violence has grown in recent months, with the country spiraling toward civil war and activists saying more than 13,000 people have been killed.

Last week, Western nations expelled Syrian diplomats in a coordinated move after a May 25 massacre in which 108 people were slaughtered in al-Houla, a cluster of small villages in the central province of Homs. The U.N. says pro-regime gunmen were believed to be responsible for at least some of the killings, but Assad has insisted his forces had nothing to do it.

Foreign Ministry spokesman Jihad Makdissi said Damascus has decided to take a “reciprocal measure” against ambassadors from the U.S., Britain, Turkey, Switzerland, France, Italy and Spain. A number of French, German, Canadian, Bulgarian and Belgian diplomats also are affected, Makdissi said, according to AP.