EU helpless to stop Nagorno-Karabakh war

"Unfortunately, at this point, further escalation and involvement of regional actors cannot be excluded," he added.

The EU did not even know what was really happening on the ground, he noted, due to a fog of disinformation and the absence of international monitors.

And Borrell rounded on MEPs calling for EU "action", saying there was little more he could do than issue statements and work the phones to plead for a ceasefire and to avoid civilian casualties.

"What do you mean by saying we have to act? We do what we can do ... If any of you [MEPs] mean military intervention - it's completely out of the question", he said.

France, along with Russia and the US, co-chairs a diplomatic peace forum on the conflict called the Minsk Group.

And Borrell said Minsk Group talks were the only way to end violence, because it was the only structure Armenia and Azerbaijan recognised.

But he admitted that even this bore little hope.

"This negotiating format has been open for the last 30 years - 30 - without any kind of advance," he said.

Several MEPs urged the EU to take a tough line on Turkey, which stands accused of supplying drones and Syrian mercenaries to Azerbaijan, its ally.

But Borrell ruled out new sanctions on Ankara until an EU summit in December, which was to "take stock" of "how to continue our relations with Turkey", in light, also, of other clashes with EU states over and oil and gas drilling in the eastern Mediterranean.

The European Parliament debate unfolded amid ongoing shelling in the South Caucasus.

Fighting has claimed hundreds of military and civilian lives in the past two weeks in the worst flare-up since full-scale war ended in 1994.

And the rhetoric being used by both sides was designed to "mobilise domestic actors" and "pull in regional ones", Borrell warned.

"To me, there is no doubt that this is a policy of continuing the Armenian genocide and a policy of reinstating the Turkish empire," Armenian prime minister Nikol Pashinyan told the Sky News broadcaster the same day, referring to Turkey's involvement in Nagorno-Karabakh.

For their part, Iran and Russia likewise warned of escalation.

The conflict was becoming a "regional war", Iranian president Hassan Rouhani told Iranian state media on Wednesday.

"Iran will not allow anyone ... to bring terrorists that Iran has fought for years to our border," he added, referring to Turkey's Syrian brigades in Azerbaijan.

Nagorno-Karabakh was becoming a magnet for jihadist mercenaries and "a new launch pad for international terrorist organisations", Sergei Naryshkin, the head of Russia's foreign intelligence service, the SVR, said on Tuesday.

"We are talking about hundreds and already even thousands of radicals hoping to earn money in a new Karabakh war," he said.

The Syrian president, Bashar al-Assad, also attacked Turkish president Recep Tayyip Erdoğan, calling him "the main instigator and the initiator" of the war.

Erdoğan logic

But Erdoğan showed no sign of backing off, in what Borrell called Turkey's "stronger and more assertive posture" and which the EU diplomat linked to a dial-down of US interest in the South Caucasus region.

Erdoğan's "logic" was to destabilise the Minsk Group because Turkey had no say in the existing structure for Galip Dalay, an expert at the Robert Bosch Academy in Berlin.

"Turkey's logic in almost all corners of the map is disruption. Anything that undermines the status quo is good for it, because the previous status quo was seen to counter its interests," Dalay told the Reuters news agency.

And Erdoğan's domestic popularity went up over his recent EU clash on oil and gas drilling, a recent poll showed.

"All of these conflicts out there boost the perception that Turkey is a country under siege, rightly or wrongly," Sinan Ülgen, from the Istanbul-based think-tank EDAM, said.