A bomb is released from a Russian Su-34 strike fighter in Syria. (Russian Defense Ministry Press Service via AP)

Russian airstrikes continued in Syria despite a shaky truce between factions fighting on the ground, according to a report published Monday. Though said to be hitting terrorist factions, some strikes have reportedly struck U.S.-backed opposition groups.

The report, written by the Institute for the Study of War, compiles data based on open-source data including “local Syrian activist networks, Syrian state-run media, and statements by Russian and Western officials.”

According to the report, there was a lull in strikes Saturday — the day the cessation of hostilities was supposed to go into affect — but they  began again in earnest Sunday. In the hours leading up to the pause, reports on the ground indicated that there were more than 100 airstrikes in northern Aleppo as Russian and Syrian government forces attempted to consolidate last-minute gains.

(Courtesy ISW)

(Courtesy ISW)

The Russian Ministry of Defense had pledged a 24-hour cease-fire after the beginning of the truce but reserved its right to continue to attack the Islamic State and Syria’s al-Qaeda offshoot Jabhat al-Nusra during the course of the two-week cessation of hostilities. In concert with its pledge, Russia released a map with designated “green-zones” highlighting where its air forces would not strike. The green zones, according to the Russian Ministry of Defense, correspond with Syrian opposition groups that had signed on to partake in the cease-fire.

In the past, Russia has made little effort to parse between the Islamic State, al-Nusra and opposition groups as its sorties have been primarily in support of Syrian government forces who are fighting elements of each.

(Courtesy ISW)

According to Genevieve Casagrande, one of the report’s authors, Russian airstrikes have been mostly limited to areas outside of their self-declared “green zone,” but that there had been reports of Russian strikes hitting U.S.-backed groups in Hama Province on Monday.

“If anything, they’re not just targeting Jabhat al-Nusra [and the Islamic State] like they’re claiming, and that’s for certain,” Casagrande said. “It’s by no means a nationwide cease-fire.”

Yet the cease-fire, by and large, has held up throughout the past 48 hours. There have been various reports of artillery and small-arms fire throughout the country, but as The Washington Post’s Liz Sly point’s out, “the intensity of the fighting appeared to have eased significantly.”

According to Cassagrande, however, if strikes continue to hit groups not affiliated with al-Nusra or the Islamic State, the cease-fire could eventually break down and “ultimately threaten any sustainable cease-fire agreement in the long term.”