Islamic State group fighters have re-entered Palmyra, nine months after losing the ancient Syrian desert city, activists say.
IS held Palmyra and its nearby ruins for 10 months before it was recaptured by Syrian government forces in March.
But the jihadist group launched an offensive earlier this week.
Meanwhile, Russian-backed Syrian government forces are closing in on the remaining rebel-held area of the city of Aleppo.
Civilians are said to be streaming out of the city in large numbers.
US Secretary of State John Kerry, speaking after a meeting in Paris of governments that back the Syrian opposition, urged Syria and Russia to “show a little grace” as they neared their objective.
Lightning offensive
Syrian government forces were backed by the Russian military when they recaptured Palmyra and its famed ancient Roman ruins from IS earlier this year.
The two militaries have since turned their attention to fighting local opposition forces in Aleppo and Damascus, Associated Press reports.
The activist-run Palmyra Co-ordination Collective said IS militants had seized the city’s military warehouse and its northern and western districts after taking government positions, oilfields and strategic heights in the surrounding countryside in a three-day campaign.
The British-based Syrian Observatory for Human Rights said IS fighters had reached the city’s hospital and its strategically located wheat silos.
“IS entered Palmyra on Saturday and now occupies its north-west,” said Rami Abdel Rahman of the Syrian Observatory for Human Rights.
“There is also fighting with the army in the city centre,” he added.
IS destroyed a number of monuments and beheaded the archaeological director during its 10-month occupation of the Unesco World Heritage site and the adjacent city of Tadmur.
Two 2,000-year-old temples, an arch and funerary towers were left in ruins.
The jihadist group, which has also demolished several pre-Islamic sites in neighbouring Iraq, believes that such structures are idolatrous.
While some treasured monuments were destroyed, much of the historic site was left undamaged.
The city was reclaimed with the support of air strikes by the Russian air force.
IS subsequently lost large amounts of territory across Syria and Iraq.
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