The two towns of Nubul and Zahraa, with an estimated 60,000 population, are connected to the border by areas under the control of Kurdish militias that provided them some access.

Al Manar, television channel of Lebanon's Hezbollah militant group, joined Syria's army and state media in reporting the breakthrough, which it said came after the army moved in from towns secured in a recent offensive in northern Aleppo province.

A Levant Front rebel said the siege was broken "after three days of legendary resistance by the revolutionaries facing the Russian military machine, an after more than 500 raids by Russian air planes".

"Less than 3 km separate the regime from cutting all routes to opposition-held Aleppo," said Rami Abdulrahman, head of the Syrian Observatory for Human Rights, said. "It did in three days what it failed to do in 3-1/2 years."