Tens of thousands of people are fleeing Syria’s third-largest city Homs amid reports that rebels are closing in, just over a week since they launched their lightning offensive.

The rebels seized Hama to the north on Thursday, a second major blow to President Bashar al Assad who lost control of Aleppo last week.

The leader of the Islamist militant group Hayat Tahrir al-Sham (HTS), Abu Mohammed al-Jawlani, told residents of Homs “your time has come”.

Rebel forces began the biggest offensive against Syria’s government in years last week.

They have been advancing south, and Homs would be the next stop on the road to the capital Damascus.

Their offensive is the swiftest battlefield advance by either side since the Syrian civil war began 13 years ago, exposing the weakness of the country’s military.

Terrified members of President Assad’s Alawite minority community are rushing to leave Homs, with video footage showing roads jammed with cars.

The rebels’ joint operations centre says its fighters have passed through two towns on the way to Homs – Rastan and Talbisseh – and are now within 5km (3.1 miles) of the city.

The BBC has not been able to verify these movements, but the Syrian Observatory for Human Rights (SOHR), a UK-based war monitor, is also reporting them.

Earlier, the SOHR said Russian warplanes had bombed a bridge in Rastan to try and slow the rebel advance.

After the Syrian military lost control of Hama following days of fighting, it is not clear whether it will be able to defend Homs.

Homs is a strategic city that links Damascus to the Alawite heartland on the Mediterranean coast, Assad’s political stronghold and key to his grip on power.

Assad has vowed to “crush” the rebels and accused Western powers of trying to redraw the map of the region

But analysts say Assad’s forces are demoralised, dealing with low pay and corruption in the ranks. Assad announced a 50% pay rise in recent days, according to state news agency SANA.

Russia and Iran, the regime’s most important allies, have declared continued support for Assad, but have not provided the kind of military assistance that so far has been propping up his rule.

The Kremlin is preoccupied with its war in Ukraine, and Iran has been weakened by Israel’s punishing campaign against its most powerful allied militia, Lebanon’s Hezbollah.

Hezbollah fighters had been key to holding regime territory in Syria.

Russian and Iranian officials are expected to meet with their Turkish counterparts at the weekend to discuss a response to this upsurge in Syria’s civil war.

Turkey backs some of the rebel groups taking part in the offensive, which analysts say almost certainly could not have happened without Ankara’s knowledge and approval.

The Turkish president Recip Tayyip Erdogan has for months pressed Assad to reach a political solution with the opposition.

Erdogan has repeated that demand now and said Turkey is working to pave the way for such an outcome.

For his part, the leader of HTS, Abu Mohammed al-Jawlani, has been making public remarks to soften his image and reassure both Syrians and foreign leaders.

He has emphasized his split years ago from Islamic State and Al Qaeda, presenting himself as a nationalist opposed to attacks outside Syria, and promising protection for minority communities.

More than half a million people have been killed since a civil war erupted in 2011 after Assad’s government cracked down violently on peaceful pro-democracy protests.

Since this offensive began nine days ago, the SOHR says more than 820 people, including 111 civilians, have been killed across the country.

Earlier, HTS fighters and their allies took over Hama and released inmates from its central prison amid fierce battles, while the military said it had redeployed troops outside the city.

Hama is home to one million people and is 110km (70 miles) south of Aleppo, which the rebels captured last week.

Meanwhile the UN has said the fighting is also “worsening an already horrific situation for civilians in the north of the county”.

An estimated 280,000 people have been displaced, most of them women and children, and some civilians are trapped in front-line areas unable to reach safer locations.

In Aleppo, a city of two million people, some public services and critical facilities – including hospitals, bakeries, power stations, water, internet and telecommunications – are disrupted or non-functional because of shortages of supplies and personnel.

UN Secretary-General Antonio Guterres urged “all those with influence to do their part” to end the civil war.