The fighting around Hama follows a rapid offensive by the militants, who, in just days, captured large chunks of territory, including Syria's second city, Aleppo, from Syria's control.

Strategically located in central Syria, Hama is crucial for the army's efforts to protect the capital, Damascus.

By late Wednesday, the Syrian Observatory for Human Rights monitor, close to the insurgents, said Islamist militants had "surrounded Hama city from three sides," but Ahram Online cannot verify this from an independent source.

"Violent clashes took place during the night" between the Syrian Arab Army and the Islamist militants, particularly in the Jabal Zayn al-Abidin area, just north of Hama, said the Britain-based monitor.

The head of the Observatory, Rami Abdel Rahman, said the Syrian army was engaged in "fierce resistance and trying to stop the rebels' advance."

The insurgents told AP that they had entered parts of the central city of Hama on Thursday.

Hama is one of the few cities that remained under full government control during Syria's civil war, which broke out in March 2011.

Syrian state media quoted a military source late Wednesday as saying Russian and Syrian air forces, alongside artillery units, had conducted "concentrated strikes on the... terrorists" in the Hama area.

Maya, a 22-year-old student who gave her first name only for security concerns, said she and her family were staying at home as the fighting rages outside.

"We have been hearing non-stop the sounds of explosions and shelling," she told AFP by telephone from Hama.

"We don't know what's going on outside."

In Aleppo's Citadel
 

The Observatory, which relies on a network of sources in Syria, says 704 people, mostly combatants but also 110 civilians, have been killed in Syria since last week.

It marks the most intense fighting since 2020.

Key to the Islamist militants' successes since the start of the offensive last week was the takeover of Aleppo, which, in more than a decade of war, had never entirely fallen out of government hands.

The head of the Islamist militant Hayat Tahrir al-Sham (HTS), Abu Mohammad al-Jolani, on Wednesday visited Aleppo's landmark citadel.

While the advancing Insurgents found little resistance earlier in their offensive, the fighting around Hama has been especially fierce.

Syrian government ordered a 50-per cent raise in career soldiers' pay, state news agency SANA reported.

The Observatory said the Syrian army brought "large military convoys to Hama" and its outskirts.