By Simon Zekaria

LONDON--BT Group PLC (BT.A.LN) Tuesday said its subscribers who take its pay-television service will have access to 351 matches from the UEFA Champions League and Europa League soccer competitions next season, as U.K. broadcasters raise the stakes to win viewers.

"We have opened the market to millions of new customers," said Chief Executive John Petter.

Telecommunications giant BT has paid billions of dollars to secure key British and European soccer television rights and bulk up its sports channels. BT's sports-broadcasting platform is a key strategic play to leverage its core broadband telephony business and compensate for declining fixed-line customers, while also bringing stiff competition to pay-TV giant Sky PLC (SKY.LN).

BT paid nearly 900 million pounds ($1.38 billion) for European soccer rights, previously held by Sky and over-the-air broadcaster ITV PLC (ITV.LN).

BT has also agreed to buy mobile operator EE to spook rivals in the U.K.'s rapidly-advancing market of combined telephony, broadband and TV services.

"[BT] has raised the stakes and Sky will need to respond. Within a short period of time, BT has proved to be highly disruptive and we expect the company to continue innovating and challenge Sky for access to more premium sports content," said CCS Insight analyst Paolo Pescatore.

"It represents a statement of intent and underlines the scale and ambition to be a leading media and telecoms provider in the U.K."

Barney Francis, managing director of Sky Sports, said Sky's audience for the Champions League European soccer competition fell 36% last season, with domestic soccer driving viewing figures. "Overall, Champions League accounts for just 2.5% of Sky Sports viewing, while the [English] Premier League is seven times bigger," he said in a recent statement.

Sky has the lion share of live broadcasting rights for English Premier League soccer matches for 2016 to 2019, paying GBP.39 billion in each of the three years of the new agreement, an 83% increase over the cost of its existing contract.

--Write to Simon Zekaria at simon.zekaria@wsj.com

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