BEIRUT (Reuters) - Rebel groups fighting in Syria's northern Aleppo province have agreed to form an alliance, a group monitoring the country's civil war said on Thursday.
A lack of unity among Syria's opposition groups has undermined the revolt against President Bashar al-Assad and made foreign powers wary of intervening in a conflict now in its fourth year.
Many of the strongest factions are hardline Islamists such as Islamic State and the Nusra Front, al Qaeda's affiliate in Syria, who have clashed with one another and with more secular rebel groups.
The fight for the nothern city of Aleppo, divided between rebels and government forces, is seen as one of the most significant last fronts for "moderate" opposition forces in the country's north.
The British-based Syrian Observatory for Human Rights said a number of armed groups in Aleppo had agreed to the alliance, including factions from the Islamic Front, which was a merger of rebel groups announced last year.
The Mujahideen Army, the Noureddin al-Zinki Brigades and other groups also agreed to the unification, it said.
The groups announced a "total merger under one flag and united leadership", the Observatory said. It said the group would be called the Shamiyya Front.
(Reporting by Alexander Dziadosz; editing by Andrew Roche)