Syrian activists say clashes between government forces and rebels are continuing in Aleppo, as the military presses on with an assault on opposition-held areas of the country's largest city.

The Local Coordination Committees and the Syrian Observatory for Human Rights reports fighting in several districts of Aleppo.

The Syrian military launched a two-pronged attack on the city Wednesday, with jets and helicopters bombing from overhead, while ground forces targeted rebel positions.

Also Thursday, Syrian President Bashar al-Assad appointed Wael al-Halqi as the new prime minister, following the defection earlier this week of former prime minister Riad Hijab.

Meanwhile, Syrian ally Iran is hosting talks in Tehran with representatives from nearly 30 countries – including Russia, Pakistan, Afghanistan and Iraq – to try to advance a solution to the crisis.

Iranian Foreign Minister Ali Akbar Salehi says the countries are committed to implementing an immediate cease-fire, sending humanitarian aid to Syria and preparing for dialogue.

The United States and its Western allies are not attending and have dismissed the conference as an attempt to divert attention away from the violence in Syria.