Turkey's state-run news agency says five people with alleged links to the Islamic State group have been detained, suspected of planning "sensational attacks" in the run-up to Sunday's referendum.

Police conducted three simultaneous operations in Istanbul Friday following a tip, according to Anadolu news agency.

A Tajik national who has traveled to "conflict zones" and who works for IS in Istanbul is among the detained, reports the agency.

IS has called for attacks against the referendum in its Arabic and Turkish publications this month, arguing that voting is opposing God and branding Muslim voters as "disbelievers."

Turkey is holding a referendum on constitutional amendments that would expand presidential powers.