Uzbek military forces crossed the Tajik border on Monday, to take part in joint Russian-Tajik-Uzbek drills close to the territory of Afghanistan, Reuters reported. 

The military exercises are to take place from August 5 to August 10 according to Uzbekistan's Ministry of Defense. 

Moscow said it would send a much bigger military contingent to Tajikistan for trilateral exercises amid fears in both countries over a worsening security situation in Afghanistan that could spill over into Central Asia. 

Security has rapidly deteriorated in Afghanistan amid the US troop withdrawal. Moscow fears that could destabilize its southern defensive flank and push refugees into its Central Asian backyard. 

On Monday, Russia's defense ministry said that 1,800 of its soldiers would take part in the Tajik drills, instead of 1,000 as initially planned. More than 2,500 troops would be involved in total, it said. 

Moscow will also use 420 units of military hardware for the drills, double the quantity originally planned, it said.