Former Iraqi border guard officer Yasin al-Muadidi has been appointed a new high-raking military leader of the Islamic State of Iraq and Syria (ISIS) extremist group, according to Russia’s RIA Novosti news agency.

Meanwhile Iraqi media outlets reported on September 3 that Tajik fugitive police commander Gulmurod Halimov had recently been appointed high-ranking ISIS military commander, replacing Abu Omar al-Shishani, who was reportedly killed in July in northern Iraq.

RIA Novosti reports that ISIS leaders have gathered in Anbar Province and elected militant Yasin al-Muadidi, known by his nom de guerre Abu Takha, high-ranking ISIS military commander.

Yasin al-Muadidi, who had military rank of Brigadier General in the Iraqi Army, reportedly joined ISIS extremist group five years ago.     

Meanwhile, Tajik authorities are reportedly investigating threats purportedly made by a former Tajik police colonel who joined the Islamic State (IS) extremist group in Syria.

The Reuters news agency quoted two Tajik security service sources as saying on September 6 that some Tajik servicemen received text messages on their mobile phones in fugitive police commander Gulmurod Halimov's name.

In the messages -- allegedly received in early September -- he promised to "congratulate" the servicemen on Tajikistan's Independence Day on September 9, the sources told Reuters.

On August 30, the U.S. State Department called Halimov a key member of IS and offered a reward of $3 million for information on his whereabouts.

Tajik authorities said on September 5 that they are taking measures to prevent any destabilization attempts in Tajikistan by Halimov and his supporters.

Halimov, the former commander of the Tajik Interior Ministry's special unit, known as OMON, joined IS in April 2015.

Tajik authorities say he has been seriously injured twice in Syria.