The Syrian Observatory for Human Rights reported Sunday that at least 400 civilians -- including families of pro-regime fighters -- had been abducted by ISIS during the latest fighting and taken to the surrounding countryside. The Observatory said it was feared they had been executed. Syria's official news agency SANA provided similar figures, claiming that ISIS had "committed a massacre in al-Bagaliyeh," a village to the north of the city, killing "around 300 civilians, most of them women, children, and elderly people."
On Monday, SANA reported, Syria's Foreign Ministry delivered letters to United Nations Secretary-General Ban Ki-moon and the U.N. Security Council, accusing ISIS fighters of "breaking into houses and homes and murdering, slaughtering, and shooting innocent civilians" and abducting others.
There is no way to independently verify the reports by the Observatory and SANA; other opposition outlets have put the number of casualties lower.
The Observatory also reported Saturday that ISIS had killed or executed some 50 soldiers and 85 civilians during its offensive against al-Bagaliyeh. ISIS deployed several suicide bombers in the attacks, in which regime positions at a hotel on the banks of the Euphrates -- the Furat Cham Palace -- were overrun.
The ISIS-affiliated news agency Aamaq said Sunday that 167 regime fighters had been killed and many more wounded. A video released by ISIS Sunday purported to show heavy artillery and tanks being used as well as abandoned regime positions.
The Observatory said that regime forces were now trying to reinforce their defenses with additional troops. And the regime-appointed governor of Deir Ezzor province, Mohammad Qaddur Ajnyyja, is reported to have told the Russian news outlet Sputnik that the Syrian army had retaken al-Bagaliyeh. There is no way to confirm his claim.
Fighting between government and ISIS forces continued Monday, the Observatory reported.
Most of the city has been controlled by ISIS for well over a year, but some neighborhoods and the military airport to the south have remained in the hands of the regime. Fighting in and around Deir Ezzor has become more intense since last October, when ISIS seized a number of checkpoints close to that airport. Inside the city, ISIS has been chipping away at the Syrian regime's remaining positions, tunneling under them and attacking checkpoints with suicide bombs.
In recent weeks, ISIS has stepped up offensives against several of these areas. And in the last few days it has overrun several neighborhoods, capturing and killing dozens of Syrian soldiers but also seizing many civilians, according to reports from activists.
Deir Ezzor is a critical junction for the group, with roads east and south toward Iraq and west to areas it controls in Homs province, including Palmyra. It is also surrounded by some of ISIS' most valuable oil fields, which have been intensively targeted by both U.S. and Russian air power in recent months. According to ISIS videos, foreign fighters have had a prominent presence in the city.
As ISIS has gone on the offensive, Russia has stepped up its support for the regime in and around the city. Russian cargo planes dropped humanitarian aid to besieged areas controlled by the regime last week, while airstrikes pounded ISIS positions. In its latest communiqué, ISIS claimed the Russians had launched 150 airstrikes on the area in 48 hours.
As the situation has worsened, some civilians have managed to escape the city, which had nearly 1.5 million inhabitants before the Syrian conflict began. One family told CNN that an elderly relative had been evacuated from the city to Damascus for $5,000 when his medical condition worsened. But he died a week later.
Neighborhoods where the regime is holding out have been under siege by ISIS for a year, with medical supplies and food scarce and generators the only source of electricity. The Syrian Observatory for Human Rights has reported massive price inflation, as products had to be smuggled across the Euphrates River.
Neither the regime nor ISIS has allowed civilians to move between the rival areas, and the Observatory reported that dozens of young men in regime-held districts joined militias because they were desperate for income.
Neither side can afford to let the other take complete control of Deir Ezzor because of its strategic position and its proximity to Syria's main oil fields.