Rebels have moved their command base from Turkey to "liberated areas" inside Syria, they announced on Saturday as regime troops and rebels battled for control of a corridor near the border and in Aleppo city.
"The Free Syrian Army command has moved into liberated areas of Syria following arrangements made with battalions and brigades to secure these zones," FSA chief Colonel Riyadh al-Asaad said in a video posted on the Internet.
The next step would be to "liberate" the capital Damascus, he added.
Nearly 80 percent of towns and villages on the Turkish border are outside government control, and President Bashar al-Assad's portraits have been removed from many public buildings, according to the Syrian Observatory for Human Rights.
"The transfer will allow the command centre to be closer to the fighters," General Mustafa al-Sheikh, head of the military council grouping rebel chiefs, told AFP, but declining to say where the new command would be located.
Rebel-held areas of Aleppo came under regime artillery fire on Saturday, with loud explosions heard across the northern city, an AFP correspondent reported.
Troops and rebels clashed near the city centre, residents said, as snipers sowed panic.
"The battle is now between snipers," Sheikh Walid, the head of a rebel brigade in the southern Amiriya district, told an AFP correspondent who reported that only a few hundred metres (yards) separate the rival snipers.
The fighting raged in Suleiman al-Halabi, one of Aleppo's main streets, and the army prevented residents from venturing out as steady gunfire rattled the district.
At least 11 soldiers and five rebels were killed in clashes in the Orm and Kaf Jum areas of Aleppo province, near the Turkish border, the Observatory said.
"The state has no presence except for military and administrative posts" in the western region of the province in northern Syria, Observatory director Rami Abdel Rahman told AFP by telephone.
He said the regime was determined to prevent rebels linking up between western Aleppo and the neighbouring province of Idlib as this would form an extensive insurgent-held region on the border with Turkey, which supports the rebels.
In shelling of several rebel-held district of Aleppo city, five members of the same family, including children, were killed in Maysar, said Abdel Rahman, whose Britain-based monitoring group relies on a network of activists on the ground.
The Observatory said regime artillery also targeted the districts of Katergi, Shaar, Sakhur, Hanano, Arkub and Marjeh.
In Damascus province, three women were among seven people killed when a shell hit a civilian bus and the bodies of six people killed by gunfire were found in the central Qadam neighbourhood of the capital, said the Observatory.
In the central city of Homs, where rebels remain entrenched in many areas, at least one soldier was killed near the Old City, while a civilian also died in Juret al-Shiyah district, it said.
Outside Homs, four soldiers were killed in an attack on their vehicle and a man was killed elsewhere in the province, it said, adding that three rebels died in clashes in the flashpoint town of Rastan.
Elsewhere, security forces raided the town of Hara in the southern province of Daraa and fighting broke out in the village of Dael.
National Coordination Committee for Democratic Change head Hassan Abdel Azim, meanwhile, told AFP that three members of his normally tolerated opposition group who went missing Thursday on the Damascus airport road were probably detained by Syrian intelligence.
In Beirut, the Lebanese military said "a large number" of Syrian rebels attacked one of its posts near the border with the war-torn country on Friday night, without causing casualties.
"Army reinforcements were dispatched to the area and began to pursue the gunmen, who fled after the attack towards the mountains and several border towns and villages" inside Lebanon, it said in a statement.
The Syrian Observatory gave an initial toll of at least 108 people killed nationwide on Saturday: 52 civilians, 32 soldiers and 24 rebels. It reported a total of 142 people, including 88 civilians, killed on Friday.
The opposition Syrian National Council warned on Friday that the deadly conflict which broke out in March 2011 was reaching "a point of extreme gravity" that could trigger higher levels of extremism in neighbouring states.
According to the Observatory, at least 29,000 people have been killed since the revolt against Assad's rule erupted.
As the violence raged, a top NATO general said the alliance does not believe military intervention would bring any improvement in Syria's security situation.
Germany's Manfred Lange said the "political process has to be pushed forward, sanctions need to take effect. At the moment, this situation cannot be solved by the military in a responsible way."