(Reuters) - Insurer Aetna Inc will buy rival Coventry Health Care Inc for $5.7 billion in cash and stock, the latest in a string of multi-billion-dollar acquisitions in the U.S. healthcare sector.

Aetna will pay $27.30 in cash and 0.3885 shares for each Coventry share held, a total value of $42.08 per share. The deal is at a 20.4 percent premium to the stock's Friday closing price.

(Reporting by Adithya Venkatesan in Bangalore)