Islamic State group jihadists launched a fierce assault Saturday in a bid to gain control of a strategic town in Syria's northeastern Hasakeh province, a monitoring group said.
In Hama province, meanwhile, government forces conducted air strikes on an IS convoy, killing 26 jihadists, including a senior local commander, the Syrian Observatory for Human rights said.
The IS offensive on the Hasakeh town of Tal Tamr "has advanced in several surrounding areas," Observatory head Rami Abdel Rahman told AFP.
"Kurdish fighters supported by Assyrian militia have fought them off in Tal Nasri," just south of Tal Tamr, killing at least eight IS fighters, he said.
Two civilians were also killed.
Assyrian Christian fighters withdrew from some areas to Tal Tamr itself to join Kurdish forces defending the town, said Osama Edward, head of the Sweden-based Assyrian Network for Human Rights.
"This is the most violent offensive on the town in a long time," he told AFP.
Since it began its onslaught in the province on February 23, IS has gained control of at least 10 villages around Tal Tamr, which lies about 40 kilometres (25 miles) south of the Turkish border and is under Kurdish control.
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If Tal Tamr falls, IS would dominate a key road in Hasakeh province that links to their bastion to the east in Iraq's second city of Mosul.
In February, IS kidnapped 220 Assyrians from areas neighbouring the town, prompting 5,000 people to flee the countryside in fear of the jihadist advance.
So far, 23 of the kidnapped have been released in exchange for a "jizya," or tax paid by non-Muslims.
Before Syria's conflict erupted in March 2011, there were roughly 30,000 Assyrians in the country, out of about 1.2 million Christians.
In Hama province, a "special operation" by government forces destroyed dozens of vehicles in an IS military convoy, Syrian news agency SANA said.
Quoting an unnamed security source, the agency said Syria's air force struck the vehicles, killing among others Deeb al-Oteibi, one of IS's self-declared provincial governors.
The Observatory said there were regime air strikes in the area on Friday and Saturday, but it was not clear when the commander had been killed.
Most of the central province is under the control of President Bashar al-Assad's regime, but significant areas, including the suburbs of the provincial capital, are held by IS and other rebel groups.