The Syrian Kurdish forces had been holding more than 10,000 IS members, but they said they are being forced to abandon some of those positions to fight the Turkish invasion.
The Kurdish forces targeted by Turkey were the US-led coalition's main ground partner in years of battle against the militant Islamic State (IS) group and its now-defunct "caliphate".
Eight more civilians were killed and 35 others were injured in southeastern Turkey on October 11 in a YPG mortar attack from across the border in northern Syria. It said the total number of Kurdish fighters killed so far numbers 277.
During the same briefing, Chairman of the Joint Chiefs of Staff General Mark Milley said there were no signs that Turkey was going to stop its offensive, though the Turkish ground incursion had been limited for now.
Turkish officials said the Kurds have fired dozens of mortars into Turkish border towns the past two days, including Akcakale, killing at least six civilians, including a 9-month-old boy and three girls under 15.
Erdogan sees the PKK - the Kurdish group linked to the SDF and classified as a terrorist group by both Turkey and the United States - as an "existential threat to Turkish territorial integrity, and he's not concerned about Western opinion for this reason", added Reilly Barry, a Turkey researcher at Harvard University.
Turkey says it is fighting to establish a "safe zone" between its borders and the Kurdish-led Syrian Democratic Forces, a US -backed military group Turkey sees as a terrorist organization.
Also on Friday, Russian President Vladimir Putin said he was anxious that as Turkish forces attack Kurdish troops, IS militants there would be able to "simply run away". Turkish and SDF forces exchanged shelling in Qamishli among other places, the SDF's Qamishlo said.
This fish can survive on land, and officials want it dead Their breathing ability makes it possible for them to navigate to other small areas of land and new bodies of water. Officials are concerned about the Northern snakehead infiltrating US water because they are 'voracious predators'.
"I'm not sure if the Turkish army can rapidly get this under control", Putin said, speaking during a visit to Turkmenistan. They hold 11,000 Islamic State detainees, of which 2,000 are foreign fighters, the official said.
Kelly Craft, the US ambassador to the United Nations, said the Trump administration does not endorse Turkey's military action and warned of unspecified "consequences", but she stopped short of condemning it.
Plumes of black smoke billowed from the Syrian border town of Tal Abyad as Turkey continued bombarding the area in an offensive that was progressing "successfully as planned", the Turkish Defence Ministry said.
"There are zones located in the north of Syria where Daesh (ISIS) militants are concentrated".
For now, Turkey's land incursion appears focused on the two towns of Ras al Ain and Tel Abyad, much further west.
Turkish President Recep Tayyip Erdogan announced the launch of the offensive, dubbed Operation Peace Spring, in northeastern Syria on Wednesday.
The president defended his decision to withdraw troops - even saying at one point the Kurds "didn't help us in the Second World War".
Turkish officials say the returns would be voluntary, insisting that the operation will provide the stability needed to create an environment for resettlement.
In response to criticism, Ismet Yilmaz, an AKP lawmaker and Turkey's former minister of defense, said the safe zone will be a "safe haven" for refugees.