- NEW: Regime forces shell some neighborhoods in Aleppo and Damascus
- Plans are under way to send 300 more fighters to bolster forces in Aleppo, commander says
- Regime forces battle rebels in several neighborhoods Friday
- A Syrian parliamentarian from Aleppo defects to Turkey
(CNN) -- Syrian rebels set up medical clinics in Aleppo apartments and homes as they braced for more clashes with government forces in the city that serves as the country's commercial hub.
Regime forces shelled some neighborhoods in Aleppo and Damascus with helicopters, according to the opposition Local Coordination Committees of Syria.
Read more: Syrian rebels seem more capable, yet still outgunned
Plans are under way to send 300 more fighters to bolster forces in Aleppo, where 18 of 22 rebel brigades are located, a rebel commander said.
As the rebels geared up for the Aleppo offensive, heavy shelling rocked other cities including Daraa, Idlib and Homs, the opposition group said.
Video: Why is Aleppo important to Syria rebels?
Regime forces battled rebels nationwide, killing at least three people, including one in Aleppo, the opposition group said.
The clashes come after at least 200 people were killed Thursday, including 48 in Aleppo and 46 in Damascus and its suburbs. The LCC said it is the first time since the uprising started that Aleppo has led in the number of deaths in a single day across Syria.
A group of Syrian refugees came under fire Thursday night while crossing the border into Jordan, said Petra, the Jordanian state news agency. A child was killed during the incident, according to Samih Maaytah, the minister of state for media affairs.
Read more: Syria's growing refugee crisis
Meanwhile, a Syrian parliamentarian from Aleppo has defected to Turkey, according to the opposition Syrian National Council. Ikhlas Badawi is the first member of the assembly elected in May to defect and the latest in a series of high-profile officials to cut ties with the regime.
The Syrian ambassador to the United Arab Emirates and his wife, who was a Syrian envoy to Cyprus, also defected, the Syrian National Council said this week. The Syrian ambassador to Iraq defected this month.
Rebel militias battling regime forces in Aleppo and other hotspots are composed largely of soldiers who have defected from the Syrian military. But there are also many civilians -- including students, shopkeepers, real-estate agents and members of the president's ruling Ba'ath party -- all trying to end four decades of al-Assad family rule.
The U.S. has expressed concerns that Syrian forces are preparing to carry out a massacre in Aleppo.
Read more: Does U.S. have a plan for post-Assad Syria?
The Syrian crisis started in March 2011 when a government crackdown on peaceful protesters morphed into a nationwide uprising against the regime.
The LCC says more than 16,000 people have been killed in the conflict. The U.N. secretary-general said this week that almost 17,000 people have died.
Read more: Faces of the Free Syrian Army
CNN's Saad Abedine and Faith Karimi contributed to this report