A problem with First Bus's mobile app is preventing customers from purchasing and activating tickets during peak periods, the company has warned.

First Bus said its mTickets App had been experiencing 'intermittent technical problems' between its busiest periods, from 7am to 9am and 5pm to 7pm.

The company, which provides bus services in Norfolk and Suffolk, said it was working to rectify the problem and that its drivers were aware of the issue.

It said: 'We're fully aware of the issue and we are working with our mTickets App service providers to rectify the problem and get normal service resumed as soon as possible.

'If you're planning to travel please rest assured that our drivers have been made aware of this situation and we'll make sure you can complete your journey.'

To obtain a refund, customers are asked to call First Bus on 0345 602 0121 and select Option 3 from the menu.

However, the company asked customers to delay their requests for 24 to 48 hours due to an expected high call volume today (Tuesday, September 4).