Syria's rebel fighters on Saturday set up a military council to unify their ranks and political opposition leaders called a meeting of all the dissident groups to forge common objectives as deadly violence swept the country.
Despite international envoy Kofi Annan travelling to Russia in a new peace push with one of Syria's few remaining allies, the army resumed heavy shelling of rebel hubs and stormed a deserter stronghold, monitors and activists said.
At least 28 civilians were killed nationwide, including two women and two children killed in the flashpoint province of Homs, the Britain-based Syrian Observatory for Human Rights monitoring group said.
Saturday's death toll also included 16 soldiers and two deserters killed in fighting, it said.
With the violence that monitors say has claimed more than 9,000 lives over the past year showing no signs of abating, the military and political opponents of President Bashar al-Assad piled the pressure on his regime.
The rebel Free Syrian Army (FSA) said it had merged with a unit led by the most senior army deserter, General Mustafa al-Sheikh, to form a united military council aimed at closing ranks in the face of the regime's unrelenting crackdown.
At the same time the main political opposition group, the Syrian National Council, invited all factions seeking to topple the Assad regime to meet in Turkey on Monday to hammer out a "national pact" of common objectives.
Speaking from Turkey, FSA chief Riad al-Asaad told AFP in Beirut that the new military council "is a step towards guaranteeing the unity of the troops and armed forces (of the opposition) on Syrian territory."
Al-Sheikh would chair the council, an FSA statement said, while a lieutenant from his unit said that Asaad would be in charge of military operations.
Asaad "will control all brigades and all (local) military councils (across Syria) must place themselves under his jurisdiction," Lieutenant Khaled Ali told AFP in Beirut.
General Al-Sheikh and 10 other generals will be tasked with deciding the military strategy of the Free Syrian Army, and will be in charge of weapons and funds, he added.
The SNC said in a statement that the aim of the two-day meeting in Istanbul was to produce a "National Pact for a New Syria," and eradicate "the regime's dictatorship."
SNC member Mohamed al-Sarmini told AFP invitations had been extended to all the factions and members of the opposition, including three prominent figures who resigned from the SNC in mid-March.
Syria's fragmented opposition has struggled to remain united in the face of the regime's deadly crackdown on dissent that began more than a year ago.
The latest announcements by the opposition come ahead of the second "Friends of Syria" conference, which world powers are due to attend on April 1 in Istanbul.
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The opposition's lack of unity and transparency has stood in the way of Western and Arab governments giving it military backing -- an option favoured however by Sunni powerhouse Saudi Arabia and Qatar.
On the ground the Syrian army rained mortar rounds on the central rebel hubs of Homs and Hama, monitors said, while the Observatory reported at least 10 civilians deaths in Homs alone.
Troops backed by 26 tanks also stormed Saraqeb in the northwestern province of Idlib, and "took up position to split the town in two," activist Nureddin al-Abdo told AFP.
Residents cowered indoors as explosions rattled Saraqeb and troops swooped to make arrests, he said from the town where there is a considerable FSA presence.
The army also used mortars to pound the town of Qalaat al-Madiq in the central province of Hama, which troops have been trying to seize for the past two weeks, the Observatory said.
Activists reported fierce overnight clashes between troops and mutineers in and around the capital, after a day of protests under the rallying cry "Damascus, here we come."
YouTube videos showed a huge night-time demonstration in the Kfar Sousa district while opposition activist Mohammed al-Shami spoke to AFP of "very violent" clashes in Damascus province with blasts heard across the city itself.
The deadly uprising that has gripped Syria for more than a year has largely spared Damascus, but has also rocked the capital in recent weeks.
Meanwhile two activists appeared in court on Saturday accused of forming a secret organisation and taking part in protests hostile to the regime, human rights lawyer Michel Shammas said, despite pledges by Assad to implement democratic reforms.
Amnesty International says thousands of regime opponents have been arrested over the past year, with many of them believed to have been tortured or otherwise ill-treated.
On the diplomatic front, UN-Arab League envoy Annan arrived in Moscow to shore up vital backing from President Dmitry Medvedev and Foreign Minister Sergei Lavrov amid signs of waning Moscow support for its Arab ally.
Annan is due to meet the Russian officials on Sunday before visiting China on Tuesday and Wednesday. Both countries have twice vetoed UN Security Council resolutions aimed at condemning Assad.
Annan is carrying with him Assad's answer to a peace plan under which Syria could begin a "political transition" to a representative government, with no specifically defined role for the Syrian leader.
His visit comes days after Moscow backed a non-binding Security Council statement in support of the initiative after making sure it contained no implicit threat of further action should Assad fail to comply.
There are growing signs that Moscow is beginning to lose patience with Assad, despite his commitment to massive new Russian arms purchases and the granting of key naval access to the Mediterranean.