The clashes on Saturday followed the deaths of 34 Kurdish rebels and two Turkish soldiers in a surge of violence earlier this week.
An ambulance driver was killed on site in the Beytussebab district of Sirnak province and three civilians wounded by mortar shells died later of their injuries at hospital, the sources said, AL Jazeera reported on Saturday.
The recent clashes broke out early Friday when outlawed Kurdistan Workers' Party (PKK) fighters launched simultaneous attacks on police and gendarmerie command posts in Beytussebab.
The earlier clashes, resulting in 36 deaths, took place on Thursday.
The Turkish army announced on Saturday that its warplanes pounded PKK shelters and depots in the Gara region of northern Iraq.
The Turkish government has waged a comprehensive "anti-terrorist" operation against the PKK since late July, with the aim of flushing the group out of its strongholds in southeastern Turkey and northern Iraq.
The PKK, designated a “terrorist organization” by Turkey and its Western allies, has hit back hard, killing dozens of police and soldiers in almost daily bomb and gunfire attacks.
Other PKK-affiliated Kurdish groups are fighting in Iraq and Syria against the Islamic State in Iraq and the Levant (ISIL).
Some of that fighting has been carried out in coordination with the US-led campaign against ISIL. Turkey is part of that campaign.
The escalation has shattered a two-year cease-fire that had raised hopes of an end to the PKK's three-decade insurgency, in which more than 40,000 people have been killed.