In a sharp escalation of Turkey's military campaign against the US-backed Syrian Kurdish YPG, on Saturday Turkish warplanes fired missiles and launched "massive bombing" of Kurdish targets in Syria's Afrin, NTV television reported.

Airstrike after airstrike pounding Afrin right now. Massive shock and awe campaign underway.



Big question is if Turkey can follow up with a competent ground campaign. pic.twitter.com/NEz8XgzwEc — Gissur Simonarson (@GissiSim) January 20, 2018

Moment where Turkish jets strike Aftin city center #Afrin pic.twitter.com/2yKtkNf8Iz — Mutlu Civiroglu (@mutludc) January 20, 2018

Turkey launches Afrin operation - LIVE COVERAGEhttps://t.co/b5jMmTwQ0M — ANADOLU AGENCY (ENG) (@anadoluagency) January 20, 2018

“The TSK (Turkish Armed Forces) has started airborne operations,” Prime Minister Binali Yildirim said at a party congress on Saturday, quoted by Hurriyet. Yildirim said eight F-16 aircraft were involved in the aerial sortie, which is ironic when one considers that Turkey is using US-made warplanes to bomb a US-backed military organization which has been provided with weapons made in the US.

Turkish jets destroyed observation posts and many other targets of PYD/PKK terrorists in Afrin, Syria https://t.co/Z8wq2L74kP pic.twitter.com/FnlF237hsZ — ANADOLU AGENCY (ENG) (@anadoluagency) January 20, 2018

NTV showing dusk shots of heavy bombardment- this mountain where we were reporting opposite of all morning until army made us all leave- had shelled several positions on mountain throughout day #afrin pic.twitter.com/fBdMBRdwA0 — Stefanie Dekker (@StefanieDekker) January 20, 2018

Despite Assad's threats to shoot down Turkish planes, Turkish air force starts aerial bombardment of Afrin Canton in northwestern #Syria pic.twitter.com/BjL26JmWAh — Michael A. Horowitz (@michaelh992) January 20, 2018

“As of this moment our brave Armed Forces have started the aerial offensive to eliminate the PYD and PKK and [Islamic State] elements in Afrin,” Yildirim said.

There have been conflicting reports whether the Turkish jets used Syrian airspace to conduct their bombing campaign.

Turkey’s General Staff officially declared the start of the military operation, calling it "Operation Olive Branch" according to a statement cited by Turkish newspaper Sol.

Operation Olive Branch

AP journalists at the Turkish border reported seeing at least five jets heading toward Afrin. Also sighted was a convoy of buses, believed to be carrying Syrian opposition fighters, and trucks mounted with machine guns.

At the same time, Reuters reports that US-backed Syrian Democratic Forces (SDF) have accused Turkey of using cross-border shelling as a false pretext to launch an offensive into Syria. The SD - an alliance of Kurdish and Arab militias fighting Islamic State - said it will have no choice but to defend itself if attacked. The alliance controls areas in Syria’s east and north.

Commenting on the offensive, Russia’s Foreign Ministry said Moscow is "carefully monitoring" the Turkish military operation, citing concerns over recent developments in the area. The ministry’s statement called on all sides in the conflict to "exercise mutual restraint" which in retrospect appears a little late.

The Russian warning comes after Turkish President Recep Tayyip Erdogan said earlier on Saturday that Ankara had “de facto” begun its operation against Kurdish forces in Afrin. He said the operation would be “followed by Manbij,” referring to the Kurdish-controlled town in northern Syria.