July 19 (Reuters) - Qualcomm Inc reported a 40 percent slump in quarterly profit, hurt in part by its escalating patent battle with Apple Inc.

Net income attributable to the company fell to $866 million, or 58 cents per share, in the third quarter ended June 25 from $1.44 billion, or 97 cents per share, a year earlier.

Revenue fell 11.1 percent to $5.4 billion. (http://bit.ly/2uAg96t)

Four Apple contractors, including Foxconn parent Hon Hai Precision Industry Co and Wistron Corp, filed a lawsuit against Qualcomm on Tuesday, alleging that it had violated two sections of a U.S. antitrust law.

The allegations are part of broader dispute between Apple and Qualcomm over the nature of Qualcomm's business model of linking the sale of chips and patent licenses. (Reporting by Rishika Sadam in Bengaluru; Editing by Anil D'Silva)