Isis has recaptured the ancient city of Palmyra in the face of heavy Russian air strikes and Syrian army resistance, nine months after it was driven from the city.

Monitoring groups the Syrian Observatory for Human Rights and the Palmyra Coordination Committee (PCC) said militants stormed the city in a multi-pronged attack on Sunday afternoon.

Russia earlier said it had helped repel the Isis assault, driving the jihadis back to orchards outside the city and killing 300 militants in the process.

But the Russian Defence Ministry later said the militants had regrouped and launched a second, more successful attempt.

They confirmed statements issued by Isis propaganda outlets claiming control of the city's 2,000 year-old Roman ruins, a Unesco World Heritage site.

The Amaq Agency said in an alert posted to the encrypted messaging service Telegram: "Breaking, Islamic State forces take complete control over Palmyra city."

The new battle for Palmyra comes almost nine months after Isis was driven out of the city at the end of March.

But this was not before they had inflicted widespread damage to the city's ancient Roman structures, including the destruction of the 2,000-year-old Temple of Bel.

Militants first overran Palmyra in May 2015, after which they forced residents of the neighbouring modern city Tadmur to live by their brutal interpretation of Sharia law.

The occupation also saw the murder of the city’s 81-year-old director of antiquities, Khaled al-Asaad, and Palmyra's ruins used as the backdrop for a series of gory executions and propaganda videos.

Isis had been advancing on Palmyra since Thursday, when the group launched a surprise attack on the Syrian army and pro-government Shia militias.

Monitors with the PCC said militants approached from “more than one axis” on Saturday, fighting their way into the al-Amiriyah district before targeting the city’s citadel.

Palmyra's Arch of Triumph recreated in Trafalgar Square Show all 5 1 /5 Palmyra's Arch of Triumph recreated in Trafalgar Square Palmyra's Arch of Triumph recreated in Trafalgar Square A replica of Palmyra's Arch of Triumph is erected in Trafalgar Square Palmyra's Arch of Triumph recreated in Trafalgar Square The original arch was destroyed by the Isis and the replica has been crafted using the latest 3D printing and carving technologies by the Institute for Digital Archaeology Palmyra's Arch of Triumph recreated in Trafalgar Square A replica of Palmyra's 2,000-year-old 'Arch of Triumph' is constructed in Trafalgar Square Getty Images Palmyra's Arch of Triumph recreated in Trafalgar Square Experts from Oxford and Harvard universities and the Institute for Digital Archaeology (IDA) built the replica arch using 3D imaging produced from photographs of the monument, which was blown up by Isis in October 2015 Getty Images Palmyra's Arch of Triumph recreated in Trafalgar Square A replica of the Palmyra's 2,000-year-old 'Arch of Triumph' in Trafalgar Square Getty Images

The same group reported that Isis had shot down a Syrian government fighter jet in nearby Jazal.

Isis has been mounting a concerted propaganda effort to highlight the campaign as its forces are beaten back in its Iraqi stronghold of Mosul.