BEIRUT (AFP) - The Syrian army advanced within firing range of the rebels' sole supply route to Aleppo in heavy fighting on Thursday despite its announcement of a ceasefire for the Eid al-Fitr holiday.
Saudi-backed rebel group Jaish al-Islam (Army of Islam) said four of its fighters were killed trying to stop the army from cutting Castello Road, the only route into rebel-held areas of Syria's second city.
Rebel fire on the government-held Sayf al-Dawla district of the city killed three people, the Syrian Observatory for Human Rights said.
The army announced on Wednesday that it was observing a 72-hour nationwide ceasefire for Eid al-Fitr, which marks the end of the Islamic holy month of Ramadan.
But fighting has continued, particularly in and around Aleppo.
President Bashar al-Assad's forces have been trying to cut Castello Road for more than two years and the Observatory said that Thursday's advance brought them the closest so far to achieving that goal.
Their capture of a hill just a kilometre away allows them to fire on any traffic moving along the road from the ground as well as from the air, the Britain-based monitoring group said.
Islamist rebels immediately launched a counter-attack but had not been able to dislodge regime fighters from the strategic hilltop.
"If government forces can hold their positions there and fight back the counter-offensive, then the opposition neighbourhoods will be completely besieged," Observatory head Rami Abdel Rahman said.
Castello Road wraps around Aleppo's eastern and northern edges then leads into rebel-controlled territory north of the battered city.
An estimated 200,000 people still live in the rebel-controlled parts of the city, which are regularly bombarded by government warplanes.
An AFP journalist in an opposition-held neighbourhood said people who had travelled into the city to visit families for the Eid holiday were stuck inside.
Syrian state news agency SANA on Thursday confirmed that regime forces were within firing range of the route after advancing in farmland north of Aleppo city.
Aleppo has been divided since mid-2012 when rebels seized the east of the city confining government forces to the west.
According to an AFP photographer in the government-controlled parts of the city, there had been intense rebel rocket fire throughout the night on the western neighbourhoods.
It had calmed by the afternoon, but few residents were venturing out.
The pre-war commercial capital has been one of the main battlegrounds of Syria's civil war and successive ceasefires announced for the city have been swiftly broken.
Syria's government has pledged to retake the whole city despite efforts by Washington and regime ally Moscow to stem the violence there.
More than 280,000 people have been killed and millions displaced since Syria's conflict erupted in March 2011 with anti-government protests.
World powers have thrown their weight behind a political settlement to the complex civil war, but UN-backed efforts to reach a transition have failed so far.
US Secretary of State John Kerry on Wednesday welcomed the 72-hour Eid ceasefire and said he was working with Russia and others to try to transform it into a lasting truce.
A landmark ceasefire announced by Russia and the United States in late February has mostly collapsed amid repeated violations.