India's HDFC Life Insurance Co Ltd reported a 15.4% rise in first-quarter profit on Friday, aided by investment gains and a rise in premium income.

The Mumbai-based company's profit after tax rose to 4.15 billion rupees ($50.6 million) for the quarter ended June 30 from 3.6 billion rupees a year ago, it said in an exchange filing.

The insurer, a unit of India's top lender HDFC Bank , reported a 13% rise in its annual premium equivalent (APE) sales, a closely watched gauge of insurance sales.

Income from investments stood at 116.29 billion rupees, compared with a loss of 33.03 billion rupees a year ago.

Earlier this week, rival ICICI Prudential also reported a profit rise on the back of the gains in securities it invested.

Industry sales of policies dropped year-on-year for each of the three months in the quarter, following government proposals to withdraw tax incentives on insurance policies from April, but narrowed sequentially, data from the insurance regulatory body showed.

Still, HDFC Life's net premium income rose 16.5% to 114.8 billion rupees.

The company's value of new business, which measures expected profit from new premiums and is a key gauge for growth, was up 18%.

In June, Indian regulators allowed HDFC Life's former parent HDFC Ltd to transfer its majority 49% stake in the insurer to HDFC Bank. Earlier this month, HDFC merged with HDFC Bank in a $40 billion deal. ($1 = 81.9925 Indian rupees) (Reporting by Biplob Kumar Das in Bengaluru; Editing by Dhanya Ann Thoppil)