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The latest developments in Russia’s war on Ukraine. All times EST.

1:15 a.m.: The Iskander tactical missile systems and the S-400 air defense systems that Russia has deployed to Belarus are fully prepared to perform their intended tasks, a senior Belarusian defense ministry official said on Sunday, according to Reuters.

“Our servicemen, crews have fully completed their training in the joint combat training centers of the armed forces of the Russian Federation and the Republic of Belarus,” Leonid Kasinsky, head of the Main Directorate of Ideology at the ministry, said in a video posted on the Telegram messaging app.

“These types of weapons (Iskander and S-400 systems) are on combat duty today and they are fully prepared to perform tasks for their intended purpose.”

It is not clear how many of the Iskander systems – which are capable of carrying nuclear weapons – have been deployed to Belarus after Russian President Vladimir Putin said in June that Moscow would supply Minsk with them and the air defense systems.

12:30 a.m.: According to Reuters, three military personnel were killed as a result of wreckage from a Ukrainian drone falling on a military base in Russia’s Saratov region, Russian agencies reported citing the country’s defense ministry.

“On December 26, at about 01:35 Moscow time, a Ukrainian unmanned aerial vehicle was shot down at low altitude while approaching the Engels military airfield in the Saratov region,” the Russian Defense Ministry said.

“As a result of the fall of the wreckage of the drone, three Russian servicemen of the technical staff who were at the airfield were fatally wounded.”

The ministry added that aviation equipment was not damaged.

12:05 a.m.: An incident at the Engels air base in Russia’s Saratov region was being investigated but there was no damage to civilian infrastructure, a local governor said, after media reports of blasts at the base earlier on Monday, according to Reuters.

Ukrainian and Russian media outlets reported that blasts were heard after midnight at the Engels air base, hundreds of kilometers (miles) from the frontlines in Ukraine.

“There were no emergencies in residential areas of the (Engels) city,” Roman Busargin, the governor of the region, said on the Telegram messaging app.

“There is absolutely no threat to residents … Civil infrastructure facilities were not damaged. Information about the incident at a military facility is being checked by law enforcement agencies.

The RBC-Ukraine news agency reported that two explosions took place. The Russian news outlet Baza reported, citing local residents, that air raid sirens were wailing and an explosion was heard.

The air base, near the city of Saratov, about 730 km (450 miles) southeast of Moscow, was hit on December 5 in what Russia said was Ukrainian drone attacks on two Russian air bases that day.

The twin strikes dealt Moscow a major reputational blow and raised questions about why its defenses failed, analysts said, as attention turned to the use of drones in the war between neighbors.

Ukraine has never publicly claimed responsibility for attacks inside Russia, but has said, however, that such incidents are “karma” for Russia’s invasion.

Some information for this report came from Reuters.