G4s, the uk security company fending off a 3bn hostile takeover attempt by canadas gardaworld, said on friday that an us competitor allied universal security services had approached it about a potential offer.

Allied universal, a california-based security company with 200,000 staff in the us, canada, mexico and the uk, had made an expression of interest about a possible offer, g4s said in a statement.

The intervention by allied universal caps a week in which the battle between g4s and gardaworld has become increasingly acrimonious. in a series of bitter exchanges, gardaworld said that g4s was deeply troubled and needed a new owner, not a face-saving change of management or a shake-up of the board.

G4s shot back, claiming that its canadian suitor was lossmaking and needs a transformative acquisition in order to realise its aspiration to be a global company.

Gardaworld, in which private equity firm bc partners has a 51 per cent stake, has offered 190p a share for g4s, which the uk company has rejected and labelled unattractive and highly opportunistic.

In late trading on friday, shares in g4s climbed 5 per cent to 212p on the possibility that allied universals interest would turn into a firm offer. its stock has surged 38 per cent since gardaworld first made its offer public in the middle of last month. allied universal declined to comment.

Tyler tebbs, an analyst at louis capital, said that the interest from allied was a potential curveball for stephan crtier [the chief executive of gardaworld] and as a former umpire would know, he will have to improve his pitch. the big question is just how serious is allied.

Uk asset manager schroders, the biggest shareholder in g4s with a 10.4 per cent stake, has already said it is open to a deal, but only at a fair price.

If g4s is sold, it would be among the 10 largest cases of an uk public company being taken private in the past five years, according to refinitiv data. advent internationals 4bn acquisition of cobham and the $6bn purchase of the satellite company inmarsat by a group led by apax and warburg pincus are among the others.

Allied universal is backed by canadian pension fund caisse de dpt et placement du qubec, private equity company warburg pincus and j safra group, a brazilian bank.

G4s is the worlds biggest security company with 530,000 staff in 85 countries guarding embassies, sports stadiums and music events as well as providing justice services such as the management of prisons.

The group has been seeking to rebuild itself under chief executive ashley almanza following a series of crises, starting with the london olympics in 2012 when it failed to recruit enough security staff and the army had to be drafted in to compensate. it recently won a deal to operate a new 252m prison in wellingborough, northamptonshire, despite a decision last year to strip it of a contract to manage birmingham prison seven years early, after inspectors found it exceptionally violent.

Gardaworld has been on dealmaking spree, adding nine businesses in the year to january 2020. since bc partners bought its stake october 2019, it has made six acquisitions, paying about 15.2 times annualised earnings before interest and taxes.