DAMASCUS, Syria (AFP) — President Bashar al-Assad vowed yesterday to crush the 17-month rebellion against his regime and to cleanse Syria of "terrorists," as his troops engaged rebels in key battleground city Aleppo.

"The Syrian people and their government are determined to purge the country of terrorists and to fight the terrorists without respite," he was quoted by state news agency SANA as telling visiting senior Iranian envoy Saeed Jalili.

Assad had earlier appeared on television for the first time in more than two weeks in a meeting with Jalili, a top aide to Iranian supreme leader Ayatollah Ali Khamenei.

Jalili offered Assad his country's backing, saying Tehran would "never allow the resistance axis — of which Syria is an essential pillar — to break.

"What is happening in Syria is not an internal issue but a conflict between the axis of resistance on the one hand, and the regional and global enemies of this axis on the other," he added.

Iran has accused Turkey and Gulf Arab countries of arming the Syrian opposition in collusion with the US and Israel, to overthrow the Assad regime.

Jalili was previously quoted as saying "the crisis in Syria must be solved internally, through national dialogue, and not through the intervention of external forces."

He added: "The Syrian people are hostile to any plan supported by the Zionists and the US."

Later, Jalili called for an end to "all foreign intervention" in Syria, adding that Tehran rejects "any party imposing its will through military intervention."

Assad said his country was "able to defeat foreign plans targeting the resistance axis and Syria's role in it."

Tehran also sent its foreign minister to Ankara and a letter to Washington holding them responsible for the fate of 48 kidnapped Iranians.

In Aleppo, clashes rocked several central areas of the city while the army also shelled rebel-held areas in the east, the Syrian Observatory for Human Rights said.

The fighting in and around Aleppo killed at least 20 people, the watchdog said, adding that the nationwide toll was 122.

Aleppo has been bracing for a major ground offensive after a senior security official said the army had completed a buildup of some 20,000 troops.

Near Homs in central Syria, opposition gunmen attacked an electricity company housing compound, killing 16 people, including Alawites, Christians and Sunnis, the Observatory said.

And rebels attacked an oil field in the eastern province of Deir Ezzor, triggering clashes in which four rebels and six soldiers were killed, it added.