Turkish authorities are investigating 10,000 social media users

Turkish authorities are investigating some 10,000 people on suspicion of using social media to support terrorism, the interior ministry said on Saturday, part of a wide crackdown that has alarmed rights groups and some Western allies.

Turkey, which faces security threats from Kurdish and leftist militants and the Islamic State, has sacked or suspended more than 100,000 people after an attempted military coup in July. It says the measures are necessary to root out supporters of the putsch and other terrorists.

Rights groups and some European countries have said President Tayyip Erdogan is using the current state of emergency to quash dissent. Since the coup, more than 150 media outlets have been shut down and 140 journalists arrested.

The interior ministry said on Saturday the fight against terrorism was being carried out "with determination" in social media.

In the last six months, authorities have detained 3,710 people for questioning, the ministry said. Of those, 1,656 have been formally arrested and 84 are still being questioned.

The remaining 1,970 have been released, although 1,203 of those are still being monitored, it said.

Access to social media sites such as Twitter and Facebook is commonly blocked, particularly after bombings or other deadly attacks, internet monitoring groups have said. Turkey denies that it blocks the internet, and has previously blamed outages on spikes in usage after major events.

Technical experts at watchdog groups say the blackouts on social media are intentional, aimed in part at stopping the spread of militant images and propaganda.

Access was severely disrupted after the assassination on Monday of Andrei Karlov, Russia's ambassador to Turkey.

And Twitter and YouTube have slowed since the publication on Thursday of a video in which the Islamic State group purportedly burned alive two captured Turkish soldiers.

An internet monitoring body, Turkey Blocks, also reported difficulties accessing virtual private networks which are routinely used to circumvent restrictions on access to social networks or websites.