The suspects, Bilge residents who were related to some of the victims, were also members of the Village Guard, a state-backed rural militia set up to combat Kurdish separatist fighters, officials said.
The authorities said the suspects used state-issued weapons in the attack.
About 57,000 village guards operate in Turkey's southeast.
They were established in 1985 to protect villages against attacks from the Kurdistan Workers' party (PKK), who are seeking an independent homeland in the region.
In Monday's attack, masked men stormed into the village square and opened fire on the crowd just after an imam had completed the wedding ceremony, witnesses said.
Local villagers have pointed to disputes over land, an unpaid debt and objections to the marriage of the couple as reasons for the murders.
Besir Atalay, Turkey's interior minister, said a "succession of events over the years" had led to the carnage, with "one important reason that accelerated the whole process," but declined to elaborate further.
Blood feuds are frequent in Turkey's Kurdish-populated regions, where feudal traditions are strong.
Security sources said 27 weapons had been seized from villagers since Monday to prevent revenge attacks.