Russian rocket launches UK telecom satellites
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Images released by Roscosmos showed the Soyuz rocket, launched by Europe's Arianespace, taking off against dark skies at 1248 GMT.
"We have lift-off," OneWeb, a London-headquartered company, said on Twitter.
OneWeb is working to complete the construction of a constellation of low earth orbit satellites providing enhanced broadband and other services to countries around the world.
The company is competing against billionaires Elon Musk and Jeff Bezos in the race to provide fast internet for the world's remote areas via satellites.
"Taking our constellation to a total of 254 satellites, this launch will allow us to provide complete coverage north of 50 degrees latitude by the end of the 2021," OneWeb said.