Turkish authorities gunned down a Russian Sukhoi Su-24 Tuesday, blaming it for violating Turkish airspace. Russia denied Turkey’s claims of airspace violation. Here are reactions from world leaders on the incident.

Turkish President Tayyip Erdogan

Turkish President Tayyip Erdogan said Wednesday that Turkey’s action was to defend its own security. The action was taken to defend the “rights of our brothers” in Syria, CNBC quoted the Turkish president as saying.

Erdogan said the Russian jet had been shot in Turkish airspace even though it crashed in Syria. He added that two Turkish citizens got injured as some parts of the Russian jet had fallen in Turkey as well.

Russian President Vladimir Putin

Russian President Vladimir Putin compared the incident to being “stabbed in the back.” He said Turkey was an accomplice of terrorists. He added that there was no other way to describe the incident as he mentioned the Russian military was doing “heroic work against terrorism.”

“Do they want to make NATO serve ISIS?” Al Jazeera quoted the Russian president as saying.

NATO Secretary-General Jens Stoltenberg

NATO Secretary-General Jens Stoltenberg said that NATO stands in solidarity with Ankara and supports Turkey’s territorial integrity. He asked Russia and Turkey to have “renewed contacts” to initiate “calm and de-escalation.”

"The common enemy should be ISIL [ISIS],” he said.

UN Secretary-General Ban Ki-Moon

The U.N. secretary-general Ban Ki-Moon said urgent measures should be taken to de-escalate tensions between Turkey and Russia.

According to U.N. spokesman Stephane Dujarric, the U.N. chief hopes for “a credible and thorough review of the incident” to help prevent future recurrences.

U.S. President Barack Obama

U.S. President Barack Obama said the incident pointed to “an ongoing problem” with Moscow’s operations in Syria. It shows the Russian military is very close to Turkish borders, he said.

"If Russia is directing its energies towards Daesh and ISIL, some of those conflicts or potentials for mistakes or escalation are less likely to occur,” Obama said while using a pejorative term for Islamic State.

"Turkey, like every country, has the right to defend its territory and its airspace."