Syrian rebels say they've begun to enter crucial city of Hama

Syrian rebels said on Thursday they had started pushing into Hama, a major city where pro-government forces backed by intense Russian air strikes are trying to stave off a new rebel victory and halt the lightning advance.

Rebel commander Hassan Abdul Ghany posted on social media that they'd begun to penetrate Hama. State media had earlier reported that pro-government forces had repelled an attack.

Rebels have been battling to try to enter Hama since Tuesday and there was heavy fighting overnight with the Syrian army and allied groups supported by a Russian bombardment, both sides said.

The rebels took the main northern city Aleppo last week and have since pushed south from their enclave in northwest Syria, reaching a strategic hill just north of Hama on Tuesday and advancing towards the city's east and west flanks on Wednesday.

Hama has stayed in government hands throughout the civil war, which erupted in 2011 as a rebellion against President Bashar al-Assad. Its fall to a revived insurgency would send shockwaves through Damascus and its Russian and Iranian allies.

The city lies more than a third of the way from Aleppo to Damascus and its capture would open the road to a rebel advance on Homs, the main central city that functions as a crossroads connecting Syria's most populous regions.

Hama is also critical to the control of two major towns with big minority religious communities, Muhrada which is home to many Christians and Salamiya where there are many Ismaili Muslims.