Black smoke mushroomed high over Baghouz as the sounds of gunfire, explosions and planes could be heard in a battle that the SDF has said is as good as over.
Gabriel said 25 ISIS militants had been confirmed killed so far in clashes, in addition to an unknown number of militants killed by air strikes.
White House national security adviser John Bolton defended President Donald Trump's much-scrutinized claims about the U.S. military's progress against the Islamic State.
The US-backed SDF relaunched their offensive in Baghouz on Sunday after the remaining Islamic State fighters refused to surrender.
Officials have previously deemed Trump's announcements claiming U.S. victory over ISIS as premature at the least.
"The President has been, I think, as clear as clear can be", Bolton told ABC News on Sunday. "We know that's not the case", Bolton said.
The enclave is the last bit of territory held by ISIL soldiers who have been driven from roughly one-third of Iraq and Syria over the past four years. Now it's the centre of a months-long battle between the SDF and what's left of ISIS.
Lawmakers and military officials were quick to speak out about both of these claims.
The destruction of ISIS at Baghouz will mark a milestone in the campaign against the jihadist group, bringing an end to its control of populated territory in the area straddling Iraq and Syria where it suddenly expanded in 2014 and declared a caliphate.
Gen. Joseph Votel, the top USA general overseeing military operations in the Middle East, also warned Thursday that the fight against ISIS is "far from over" despite the terror group's territorial losses and cautioned that the remnants of the group are positioning themselves for a potential resurgence.
The counterattack began from the west of a riverside pocket in the Syrian village of Baghouz where the Islamic State group has been making its last stand, said a commander with the U.S-backed Syrian Democratic Forces, or SDF.
When Raddatz asked if he agreed with Votel, Bolton said he wouldn't "criticize" the soundbites of Votel's comments.
Trump abruptly announced in December the immediate and complete withdrawal of the 2,000 USA troops deployed in northeastern Syria, declaring victory against IS, or ISIS as it is also known. The White House walked back the claim amid blowback from lawmakers in both parties.
In Syria, regional security analyst Kierat Ranautta-Sambhi writes a "trifecta of grievances" allow the group to pose a threat moving forward, as anti-Assad sentiment, sectarian cleavages in the populations, and socio-economic shortcomings may still drive local support to the group.
Bolton also spoke to "This Week" about North Korea, saying that President Trump would be "pretty disappointed" if Kim Jong-un went ahead with another ballistic missile test launch.
No Islamic State leaders are believed to be in Baghouz, according to a USA defense official.
"We are still countering the assault until this very moment", he said.