BEIRUT (Reuters) - A top aide to Iran's leader met Syrian President Bashar al-Assad on Tuesday, footage on Syrian state television showed, underlining firm Iranian support for Damascus as it faces mounting pressure from insurgents in a four-year-old civil war.
The meeting came as insurgents in Idlib province seized an army base from the Syrian military, expanding their grip in the northwest of the country, the Britain-based Syrian Observatory for Human Rights monitoring group said.
Ali Akbar Velayati, a senior adviser to Iranian Supreme Leader Ayatollah Ali Khamenei and a former foreign minister, was the most senior of three Iranian officials to travel to Damascus in less than a week.
State television said the meeting yielded several agreements in the oil, electricity and industrial sectors and regarding investments, without giving further details.
Assad told Velayati that Iran was "a main support in our battle against terrorism" while Velayati reiterated Iran's continued backing for Assad, state news agency SANA said.
"Iran is determined to continue to stand by Syria and supporting it with whatever is needed to reinforce the resistance its people are showing in defending the country and fighting terrorism," SANA quoted Velayati as saying.
Iran is Syria's most powerful regional ally and has become more pivotal to Assad's position since the uprising against his family's four-decade-old rule of Syria broke out in 2011.
Tehran has provided funds to prop up the struggling economy and Iranian military advisers are on the ground in addition to Iranian-backed Hezbollah fighters from neighboring Lebanon. The anti-Assad insurgents draw support mainly from the Gulf Arab region, led by Saudi Arabia - rivals of Iran for regional power.
On Monday Rustom Qasemi, head of an Iranian agency tasked with developing bilateral economic relations, visited Assad and said Tehran wanted to shore up Syria economically.
Lebanese newspaper As-Safir reported on Tuesday that Qasemi's visit involved completing an agreement on a new Iranian credit line for Damascus.
Alaeddin Boroujerdi, head of the Iranian parliament's national security and foreign policy committee, also reiterated Iranian support for Syria's government in a visit last week.
Last month Iran's foreign minister said Western and Arab demands for Assad's removal have fueled years of unnecessary bloodshed as they have prevented negotiations on a political settlement.
But Assad's position has been shaken over the past two months by the loss of notable areas of northwestern and southern Syria to a patchwork of insurgents including al Qaeda's Nusra Front, the Islamist Ahrar al-Sham group and mainstream, Western-backed groups.
Ultra-hardline Islamic State militants have intensified the pressure by attacking government-held areas in central Syria, closing in on the ancient heritage site of Palmyra.
Editing by Mark Heinrich