ANKARA, Jan. 23 (Xinhua) -- Some 91 suspects were detained in 13 provinces across Turkey for allegedly promoting the Syrian Kurdish Democratic Union Party (PYD) and the outlawed Kurdistan Workers' Party (PKK) on social media, state-run Anadolu Agency reported on Tuesday.

Three suspects were arrested, the agency reported.

On Sunday, investigations were launched by the chief public prosecutor's offices in Kutahya, Mardin, Diyarbakir, Mus, Mugla, Ankara, Istanbul, Izmir, Van, Agri, Mersin, Igdir, Sanliurfa, Bingol and Ardahan provinces against some social media users who allegedly voiced support to the PYD, a Kurdish group in Syria.

The detained are accused of spreading "delusive information and terror propaganda."

Anti-terrorism units carried out simultaneous operations after Turkey has launched a military operation against the Syrian Kurdish militia in Afrin province in northern Syria, across the Turkish border.

A person who was taken into custody in Agri province was arrested on charges of "making propaganda for a terrorist organization."

Two people in Mugla province's Bodrum district were also arrested on charges of "inciting people to hatred and hostility" and "making propaganda for a terrorist organization."

Pro-Kurdish People's Democratic Party (HDP) lawmaker Meral Danis Bestas, journalist Ishak Karkas and novelist Nurcan Baysal were detained for their social media posts about "Operation Olive Branch" into Afrin.

HDP Izmir Province Head Cerkez Aydemir, HDP Nusaybin District Head Ferhat Kut and pro-Kurdish Democratic Society Congress Co-chair Leyla Guven are also among the detainees.

The Turkish military has launched a cross-border land operation into the Syrian province of Afrin on Saturday to fight the Syrian Kurdish militia.

The army is targeting the People's Protection Units (YPG) elements in the Kurdish enclave with Free Syrian Army (FSA) fighters through airstrikes and land forces. YPG is the military wing of the PYD, a group in northern Syria that Ankara has deemed a "terror group" for its links to the PKK.

At the weekend, President Recep Tayyip Erdogan warned supporters of the pro-Kurdish opposition party HDP not to protest the military's operation in northern Syria, saying security forces would intervene if they demonstrated.

His warning came after HDP called on local people in eastern Van province to hit the streets against the operation.

"Know that wherever you go out on the streets, our security forces are on your necks," he said, referring to members of the HDP, parliament's second-largest opposition party. Over 10 lawmakers of the party are arrested over claims of links to the PKK.

"This is a national struggle. We would crush anybody who opposes this. There will be no compromises or tolerance on this issue," he said.

Turkish police have blocked off one of the offices of the HDP in an effort to prevent them from holding a press conference about Afrin operation.