Worldpay said it had received preliminary approaches from US payments giant Vantiv and JPMorgan.

However, the company warned "there can be no certainty either that an offer will be made nor as to the terms of any offer, if made".

Worldpay processes millions of mobile, online and in-store transactions daily.

It describes itself as a pioneer in card payments, multi-currency processing and the rapidly-growing area of online and contactless payments.

Worldpay says it is the market leader in payments in the UK, where it handles more than 40% of all transactions and employs 5,000 people at its London headquarters.

Its systems are particularly popular with small and medium-sized businesses such as hairdressers, restaurants and pubs.

Worldpay joined the London Stock Exchange two years ago and it is a member of the FTSE 100 index of the UK's largest listed companies.

It is the second time in two days a payment processor has become a bid target. Over the weekend Danish card payment services company Nets A/S said it had been approached by potential buyers, which market observers say could involve established payment giants Mastercard or Visa.

"This is one of the most intriguing sub-sectors in the financials space," said Angelo Meda, head of equities at Banor Capital.

"There are a lot of companies still, and we are probably going to have only one or two big leaders in the payments space."

Dave Birch, an analyst at Consult Hyperion, said such companies were under pressure to form bigger global businesses.

"Consolidation is widely seen as the only way forward for these businesses. There are global merchants out there who want global suppliers: they don't want one in the US and another in the UK."