"Strategies must change according to the circumstances; we cannot solve numerous global and regional issues with stagnation and employing the same tactics," he added.

Iran has been a strong ally of the Assad family, whose decades-long rule of Syria ended on the weekend when a whirlwind rebel offensive took the capital Damascus.

Assad had long played a strategic role in Iran's anti-Israel "axis of resistance", particularly in facilitating the supply of weapons to Tehran's ally Hezbollah in neighbouring Lebanon.

The axis of resistance includes Hezbollah as well as Hamas in Gaza, Huthi rebels in Yemen and some smaller Shia militia groups in Iraq.

Also on Thursday, the Islamic Revolutionary Guard Corps strongly condemned "the abuse of the current instability in Syria by the US and the Zionist regime," which is Iran's term for Israel.

"The Resistance Front will not be passive in confronting any plan or scheme that seeks to disrupt the resistance and weaken the power and authority of the countries in the region," the Revolutionary Guards said in a statement.

Turkey has forces in northern Syria, while in the south the Israeli army has sent troops into a UN-patrolled buffer zone on the countries' shared border, east of the Israeli-annexed Golan Heights.

The United States also has troops based in Syria, where they have worked with Kurdish-led fighters battling the Islamic State group.

Ties between Tehran and Damascus peaked during the Syrian civil war that started in 2011, with the Revolutionary Guards sending what it called "military advisers" to help Assad.