The rockets hit a school, two houses and a truck in the Karkamis district, near a border gate in Gaziantep province, the governor Davut Gul said, adding six had been wounded.
Interior Minister Suleyman Soylu later said three had died.
Broadcaster CNN Turk said the rockets were fired from the Kobani area of Syria, controlled by the YPG.
It comes a day after Turkish warplanes carried out air strikes on Kurdish militant bases in northern Syria and Iraq, destroying 89 targets.
The defense ministry said the operation was in retaliation for a bomb attack in Istanbul that killed six people a week ago, which authorities have blamed on the outlawed Kurdistan Workers’ Party (PKK).
As part of the weekend operations, Ankara said that 8 security personnel had been wounded in rocket attacks by the YPG from Syria’s Tal Rifat on a police post near a border gate in Turkiye’s Kilis province.