BEIRUT, Lebanon - Syrian rebels fully captured a northern town near the Turkish border Tuesday after weeks of siege and heavy fighting, activists said.

The takeover of Harem, a town of 20,000 in northern Idlib province, was the latest in a string of recent rebel successes that include the capture of wide areas along the border with Turkey. Most of those areas have been in northern Aleppo province, where antigovernment forces have captured at least three large military bases.

The Britain-based Syrian Observatory for Human Rights said that rebels captured Harem early Tuesday. Mohammed Kanaan, an Idlib-based activist, said the last post to be taken was the historic citadel, which overlooked the town. The army had turned the citadel into a military post.

"Harem is fully liberated now," Kanaan said via Skype.

Rami Abdul-Rahman, director of the Syrian Observatory for Human Rights, said nearly 30 soldiers and pro-government gunmen surrendered late Monday. He added that rebels set free all gunmen aged 16 or less and referred others to local tribunals.

"Harem was very important because it is one of the towns that was loyal to the regime," Abdul-Rahman said about the town that is nearly a mile from the Turkish border.

In Aleppo province, which neighbors Idlib, local activist Mohammed Saeed said rebels attacked a military air base in the town of Mannagh near the border with Turkey.

Regime forces have been using helicopters to carry supplies to besieged areas and to attack rebel positions.

The regime has had increasing difficulty sending supplies by land to Aleppo province after rebels in October captured the strategic town Maaret al-Numan. The town is on the highway that links Damascus with Aleppo, Syria's largest city and commercial center and a major battleground in the civil war since July.

In the Damascus suburb of Jaramana, opposition gunmen ambushed the head of military intelligence in the area and seriously wounded him. He later died of his wounds, the Observatory said.

In Israel, top officials said they cannot corroborate Syrian activists' claims that the regime has used chemical weapons against its citizens.

Vice Premier Moshe Yaalon told Army Radio that Israel had "no confirmation or proof" the regime has employed such weapons in the civil war. He said Israel was "monitoring the situation with concern."

Defense Ministry official Amos Gilad told Israel Radio that Syria was closely guarding its chemical weapons stockpiles.

On Monday, the Observatory quoted activists in the central city of Homs as saying that six rebels died in two neighborhoods the day before after inhaling white smoke that came out of shells fired by government troops in the area. Amateur videos released by activists showed men in hospital beds suffering breathing problems as doctors placed oxygen masks over their faces.