Merck & Co. Inc. said today it is buying a British biotech company, Avecia Biologics, which is working on medicines targeted at forms of cancer, heart disease and stroke.

The companies did not disclose financial terms. Merck spokesman Ian R. McConnell said Avecia Biologics, part of a holding company called Avecia Investments Ltd., employs about 500.

A Merck senior vice president, John T. McCubbins, said the acquisition was part of a strategy "of expanding our biopharmaceutical expertise and manufacturing capacity."

Merck, of Whitehouse Station, N.J., has large operations in the Philadelphia area. Merck acquired Schering-Plough Corp. in November for $41.1 billion.    - Reid Kanaley