G4S, via Bloomberg News

LONDON — G4S, the world’s biggest provider of security services, agreed Monday to buy a Danish rival, I.S.S., for about $8.2 billion to add cleaning and catering services and to accelerate its expansion in Asia and Latin America.

G4S, which is based in Britain, plans to raise £2 billion, or $3.2 billion, in a rights offering to help pay for the acquisition of I.S.S., which is owned by EQT Partners and Goldman Sachs. The price tag, which includes debt, is roughly 8.5 times I.S.S.’s earnings over the last 12 months, G4S said.

The acquisition comes about seven months after I.S.S. shelved plans for an initial public offering amid jittery financial markets. It had planned to raise an estimated $2.5 billion.

The combination would create a giant security company with about $25 billion in revenue, employing more than one million people in more than 40 countries. The company would offer clients services that included cleaning offices, which G4S said was worth billions globally.

“We believe this acquisition will transform our business, significantly accelerate the delivery of our solutions strategy and create substantial value for shareholders,” Nick Buckles, chief executive of G4S, said in a statement.

The acquisition would add to revenue in the first year and generate estimated pretax cost savings of $158 million by 2014, G4S said. In addition to the rights issue, G4S would use new debt facilities to finance the acquisition.

Mr. Buckles would remain chief executive of the combined group, and I.S.S.’s chief executive, Jeff Gravenhorst, would head the European operations. The sale is subject to approval by shareholders and regulators.

“The combination of I.S.S. and G4S is a good fit both industrially and culturally,” Ole Andersen, I.S.S.’s chairman, said in a statement. “Together they can increase their exposure to the significant growth opportunities in emerging markets and accelerate their efforts in the growing market opportunity for integrated facilities services.”

Deutsche Bank and Greenhill advised G4S on the transaction.