Turkish Firtina howitzers fired on IS targets as the contingent advanced, Dogan said.
Euphrates Shield is Ankara's most ambitious operation during the five-and-a-half-year Syria conflict, backed by the tanks as well as war planes and special forces providing support to rebels.
The goal is to remove IS from its border and to halt the westward advance of the Kurdish People's Protection Militia (YPG).
US President Barack Obama's anti-Islamic State envoy Brett McGurk said on Twitter US forces hit jihadist targets overnight on Friday with a "newly deployed" mobile rocket system close to the Turkish border with Syria.
The US embassy in Ankara said on the social media website it was the "latest step in US-Turkey cooperation in the fight against ISIL (IS)".
Meanwhile, Turkish war planes destroyed two IS targets in Wuguf in southern al-Rai between 10:00 GMT and 10:24 GMT, the Chief of Staff said, quoted by NTV television.
The statement also said two villages were captured by rebels on Saturday in the al-Rai region. In the last few months, al-Rai has repeatedly changed hands between rebels and IS.
Ahmed Othman, a commander in pro-Turkey rebel group Sultan Murad, told AFP in Beirut that his group was now "working on two fronts in al-Rai, south and east, in order to advance towards the villages recently liberated from IS west of Jarabulus".
Othman said it was the first phase of their plans. "We want to clear the border area between al-Rai and Jarabulus from IS, before advancing south towards al-Bab (the last IS bastion in Aleppo) and Manbij (controlled by pro Kurdish forces)."
After the Kurds' success in Manbij, they said they wanted to advance and link their other two "cantons" in northern Syria, Kobane and Afrin.
But Turkish President Recep Tayyip Erdogan said on Friday that Turkey would not allow the group to create a "terror corridor".
- Syrian rebels retake villages -
Ankara sees the Kurdish Democratic Union Party (PYD) and the YPG as terror groups acting as the Syrian branch of separatist rebels in Turkey's restive southeast.
Militants from the outlawed Kurdistan Workers' Party were blamed on Saturday for the deaths of 20 Turkish soldiers and a village guardsman after three separate clashes and an attack in a violent 48 hours in the country's east and southeast.
The guard killed was part of a group of local residents who cooperate with Turkish security forces against the PKK, listed as a terror group by Ankara and its Western allies.
In Cologne meanwhile, up to 30,000 people took part in a protest against the Turkish offensive in Syria, German news agency DPA reported, while calling for the PKK leader and one of its founders Abdullah Ocalan to be released from jail.
The intervention into Syria last month caused another complication in what was already a tangled five-year civil war, with Ankara and Washington supporting different proxy groups seeking to retake territory from IS.
The United States has provided training and equipment to the YPG, much to Ankara's chagrin.
Within 14 hours on August 24, Turkish-backed Syrian rebels recaptured the border town of Jarabulus from IS and continued to make gains in villages nearby.
According to the Britain-based Syrian Observatory for Human Rights, Turkey-backed rebels also took control of eight villages and two farms on both the Jarabulus front and new al-Rai front.
But Othman said the rebels had taken control of nine villages on the newest front and four on the Jarabulus front.
Observatory head Rami Abdel Rahman said that only "25 kilometres was left for the pro Turkey rebels to control the border area between al-Rai and Jarabulus".
Turkey has also carried out strikes against the YPG north of the town of Manbij, which the Kurds seized last month.