Russian President Vladimir Putin’s spokesman Dmitry Peskov said on Friday the Kremlin was in close contact with Ankara on stabilizing the situation in the South Caucasus.

He said the Kremlin will take necessary steps to ensure its security, as Turkish President Recep Tayyip Erdogan on Thursday did no rule out the construction of a Turkish military base in Azerbaijan.

“There may be development, expansion here later,” Erdogan said.

Peskov reacted to his remarks, saying, “The deployment of military infrastructure by the (NATO) alliance countries near our borders is cause for our special attention, as well as a reason for us to take steps to ensure our security and interests.”

Turkey signed a declaration with Azerbaijan in the city of Shusha, which according to Azeri President Ilham Aliyev, concerned cooperation on political, economic, trade and energy issues.

“But most important is the agreement on cooperation between Azerbaijan and Turkey in the defense industry sphere and mutual military assistance,” Aliyev said.

The city of Shusha is among the territories gained by Azerbaijan during last year’s conflict over between Azerbaijan and Armenia.

A Russian-brokered ceasefire put an end to six weeks of war between Armenia and Azerbaijan in November last year and left Azerbaijan largely in control of the territory.

The conflict killed more than 6,000 people on both sides and led to a political crisis in Armenia.

Border tensions have, however, been running high again earlier this month, after Yerevan accused Baku of sending troops across the border and violating the ceasefire.

Nagorno-Karabakh is internationally recognized as part of Azerbaijan but has been populated by ethnic Armenians.

Both Russia and Turkey deployed peacekeeping troops to the region to monitor the truce deal.

Russia has a military base in neighboring Armenia, as well.