Azerbaijan says its forces have entered the Lachin district, the last of three handed back by Armenia as part of a deal that ended six weeks of fighting over the breakaway Nagorno-Karabakh region.
"Units of the Azerbaijani Army entered the Lachin region on December 1" under the deal signed on November 9 by Armenia, Azerbaijan, and Russia, the Defense Ministry said in a statement.
The ministry also released a video showing a tank flying the Azerbaijani flag and leading a column of trucks along a road at night.
Azerbaijan lost control of Lachin during a war with Armenia in the early 1990s as they transitioned into independent countries amid the breakup of the Soviet Union.
Lachin was a strategic link between Armenia's internationally recognized border and ethnic Armenian-held areas in Nagorno-Karabakh.
Armenia agreed to hand over three districts ringing Nagorno-Karabakh -- Agdam, Kalbacar, and Lachin -- after nearly three decades under Armenian control as part of the Russian-brokered agreement signed on November 9, halting military action in and around Nagorno-Karabakh following the worst fighting in the region since the 1990s.
Agdam was ceded on November 20 and Kalbacar five days later.
Almost 2,000 Russian peacekeepers have moved into the area as part of the truce deal, including along the Lachin Corridor, an overland route linking Armenia with Nagorno-Karabakh.
The agreement also committed the parties to reopening their borders for trade but sets no time frame for that.
Ethnic Armenians in Nagorno-Karabakh have been governing their own affairs, with support from Armenia, since Azerbaijan's troops and Azeri civilians were pushed out of the region in a war that ended in a cease-fire in 1994.
Russia has extensive relations with both Armenia and Azerbaijan but provides security guarantees to the former.