According to the Wall Street Journal, Russia is recruiting Syrians adept in urban combat to fight in Ukraine as Moscow’s incursion deepens into Ukrainian cities.

“Russia, which has been operating inside Syria since 2015, has been recruiting fighters from there in recent days, hoping that their expertise in urban combat can help take Kyiv and deal a devastating blow to the Ukrainian government,” according to four US officials quoted by the Wall Street Journal.

Syrian fighters are already in Russia, according to one official, prepared to enter Ukraine.

Russia has offered volunteers between $200 and $300 to “travel to Ukraine and operate as guards” for six months at a time, according to a Syrian publication headquartered in Deir Ezzor.

The WSJ article comes three days after Russian President Vladimir Putin accused Ukrainian forces of employing human shields and fighting Russian troops on the ground with “foreign mercenaries” from the Middle East.

“The very pattern of hostilities demonstrates that we are fighting exclusively against neo-Nazis. “Nationalist and neo-Nazi forces are using citizens as a human shield,” Putin stated, adding that foreign mercenaries, including those from the Middle East, are among them.

As the Russian invasion of Ukraine enters its 12th day, foreign government officials and intelligence sources suggest Moscow’s military operations are falling behind schedule due to unanticipated pushback from Kyiv’s soldiers.

Ukraine’s government have welcomed any international volunteers willing to fight in the country.

On Sunday, International Minister Dmytro Kuleba told CNN that 20,000 foreign fighters, largely from Europe, are helping Ukraine withstand the Russian assault.

Hundreds of civilians have died as a result of the battle so far. The UN High Commissioner for Human Rights (OHCHR) reported 406 deaths and 801 injuries on Monday, suggesting that the true numbers are “considerably higher.”

“The majority of civilian casualties were caused by the employment of explosive weapons with a large effect area, such as shelling from heavy artillery and multi-launch rocket systems, as well as missile and air strikes,” according to the OHCHR.