Islamic State jihadists seized abandoned war-fighting gear after they recaptured the ancient Syrian city of Palmyra from the Russia-backed Damascus regime, the Pentagon said Tuesday.

IS overran Palmyra on Sunday, nine months after being expelled by Russian air strikes and forces loyal to President Bashar Al-Assad.

It was "probably one of the most significant counter-attacks we've seen by ISIL," Pentagon spokesman Navy Captain Jeff Davis said, using an IS acronym.

"It resulted in ISIL taking whatever material the regime left behind. That could include armored vehicles, it could include artillery."

When IS first swept across neighboring Iraq in 2014, local security forces fled with scant resistance, dumping their weapons and gear -- much of it provided by the United States.

IS first seized Palmyra in May 2015 and went on to blow up UNESCO-listed Roman-era temples and loot ancient relics. 

The Pentagon and coalition partners have accused Moscow and Damascus of taking their eye off Palmyra to focus on bombing the former rebel bastion of Aleppo.

"There could certainly be an argument made that the regime, which is backed by Russia, had been so singly focused on Aleppo that they failed to watch their six," Davis said.

He said regime troops had departed from Palmyra "very quickly" as IS moved in.

Moscow has accused the United States of failing to coordinate military efforts, thus enabling the IS counter-attack on Palmyra. 

State Department spokesman John Kirby said neither Russia nor Assad had ever been committed to fighting IS inside Syria. 

The effort "has been to violently crush the opposition, and even at the cost of so many innocent lives," he said, amid mounting global outrage over reports of atrocities as forces loyal to Assad closed in on the last pocket of rebel territory in Aleppo.

Source: AFP