The US will ban its citizens from traveling to the Democratic People's Republic of Korea (DPRK), two tourist agencies who operate tours there have said. 

Koryo Tours and Young Pioneer Tours both said the ban would be officially announced on July 27 and come into effect 30 days later. 

Neither company was able to confirm how long the travel ban would last. 

The US has not confirmed the news yet.

Young Pioneer Tours was the agency that took US student Otto Warmbier to the DPRK.

He was detained and sentenced to 15 years of hard labor last year for allegedly trying to steal a propaganda poster from his hotel.  

22-year-old Warmbier was released in June in a coma and died in hospital days after returning to the US. 

Pyongyang said through state media that Warmbier's death was "a mystery" and dismissed his parents' accusations that their son's death was a result of mistreatment in jail.  

Warmbiers' death added to tensions between Washington and Pyongyang.  

The situation further deteriorated this month after the DPRK claimed it had successfully test-fired an intercontinental ballistic missile.