The operation dubbed "Peace Spring" by the Turkish government, began on Wednesday at around 4 p.m. with air raids and shelling while a ground offensive, involving Turkish soldiers and allied Syrian rebels, began at 11.30 p.m., reports Efe news.
Turkish Vice President Fuat Oktay tweeted in early Thursday morning that the operation was going ahead as planned.
"As the operation is ongoing successfully, basic priority is not to harm the civil."
The country's Defence Ministry said the Army had destroyed 181 targets belonging to Kurdish forces, mainly ammunition dumps, on the first day of the operation.
At least 60 Turkish warplanes took part in the offensive, striking targets 30 m into Syrian territory in line with Ankara's goal to secure what it calls a "safe zone" in northern Syria.
Turkish authorities want the "safe zone" to extend some 32 km into northern Syria, stretching from the Euphrates River to the Iraqi border.
As well as using the area to re-home some of the roughly 4 million Syrian refugees in Turkey, the government wants to avoid the creation of a Kurdish statelet along its border.
Northeastern Syria, a Kurdish majority region, is currently under the control of the Kurdish People's Protection Units (YPG), a key US ally in the years-long fight against the Islamic State (IS) terror organization.
But Ankara views the YPG as indistinguishable from their more habitual enemies, the Kurdistan's Workers Party (PKK), which has fought a decades-long insurgency in southeast Turkey.
In response to the Turkish incursion into northern Syria, the YPG fired mortar rounds into Turkish towns across the border and attacked Turkish-backed factions of the Free Syrian Army - recently rebranded as the Syrian National Army - Tel Rifat and Jarablus.
Kino Gabriel, a spokesperson for the Syrian Democratic Forces, an umbrella organisation dominated by the YPG, told Efe news that a "tense calm" reigned over the border region on Thursday.
The SDF said late Wednesday that eight people, including five civil, had been killed by the Turkish military operation.
Turkish airstrikes were reported at the border towns of Tal Abyad, Ras al-Ayn and Qamilshli, as well as Ain Issa further south.
Turkish newspaper Hurriyet said one civilian was killed and seven others were injured in the Jarablus clashes.
The Free Syrian Army, formed by militants opposed to President Bashar Al Assad's regime, fought alongside Turkey on two previous invasions of northern Syria.
The YPG spearheaded the ground battle against the IS in the area with the help of US air support and military training.
Earlier this week, US President Donald Trump announced he would pull the remaining American troops from the region, effectively greenlighting Erdogan's plans to invade northern Syria.
Turkey's invasion of the region has been denounced by several countries, including the United Kingdom, France, the Netherlands, Canada and Germany as well as regional powers like Saudi Arabia, the United Arab Emirates, Jordan, Egypt and Lebanon, among others.
( With inputs from IANS )