BEIRUT – Syrian rebels fully captured a northern town near the Turkish border Tuesday after weeks of heavy fighting and attacked a regime air base in a neighboring province, activists said.

The air base is in Aleppo province, where opposition fighters have already captured three other large military bases in recent months. Rebels have also laid siege to the international airport in the city of Aleppo, Syria’s commercial capital, and launched an offensive on the police academy near the city.

With steady rebel gains across the north, President Bashar Assad’s regime is having increasing difficulty sending supplies by land to Aleppo province, especially after rebels cut a major thoroughfare from Damascus. It is just another sign that the opposition is consolidating its grip across large swaths of territory in northern Syria.

In his traditional Christmas address, Pope Benedict XVI decried the slaughter of the “defenseless” in Syria, where anti-regime activists estimate more than 40,000 have died in fighting since the uprising against Assad’s rule began in March 2011.

In another blow to the regime, activists said that Mohammed Adnan Arabo, a member of Syria’s parliament has left the country and joined the opposition. An executive council member of the opposition Syrian National Council group and other activists said Arabo arrived in Turkey on Tuesday.