The announcement comes as the British group, which goes head-to-head with Sky for live TV coverage of English Premier League football, announced a 15-percent hike in annual pre-tax profits to more than £3.0 billion.
During its 2015-16 financial year ending in March, BT completed its £12.5-billion takeover of mobile phone operator EE, previously owned by French group Orange and Deutsche Telekom.
BT said in a statement that it would “spend around six billion pounds in capital expenditure over the next three years in the first phase of a plan to extend superfast broadband and 4G coverage beyond 95 percent of the country by 2020”.
BT Group chief executive Gavin Patterson added: “The UK is a digital leader today and it is vital that it remains one in the future.”
In morning deals, BT’s share price was up 3.25 percent at 453.85 pence compared with Wednesday’s close.