ANKARA, Jan. 29 (Xinhua) -- A total of 311 suspects have been detained so far over "terrorism propaganda" on social media after Turkey started cross-border operation into Syria's Afrin, Turkish Interior Ministry said on Monday.

The chief public prosecutor's office launched investigations in six provinces, including Ankara and Istanbul, against social media users following the Turkey's military operation. At least 571 social media accounts have been inspected by police.

These suspected users are accused of voicing support for the Kurdistan Workers' Party (PKK), listed as a terrorist organization by Turkey, the U.S., and the EU, and its Syrian affiliates the Democratic Union Party (PYD).

Turkish military and the Free Syrian Army (FSA) on Jan. 20 launched "Operation Olive Branch" against militants of the Syrian Kurdish People's Protection Units (YPG) in Afrin.