By Rogerio Jelmayer 

SÃO PAULO--Brazilian mining giant Vale SA posted a net-profit increase of 17.3% in the second quarter, as lower debt-service costs helped to offset lower revenue.

Vale, the world's largest iron-ore producer, on Thursday reported a second-quarter net profit of $1.68 billion, up from $1.43 billion a year ago.

The company's debt-service costs totaled $215 million in the second quarter, down from $983 million the previous year.

Vale's net revenue dropped 29.7% to $6.96 billion.

Its earnings before interest, taxes, depreciation and amortization, or Ebitda, tumbled 46.1% in the period to $2.2 billion.

Vale was able to reduce its cost and expenses in the period, to $4.93 billion, compared with $6 billion in the second quarter of 2014.

The company invested a total of $2.1 billion in its operations in the period, down from $2.47 billion one year ago.

Vale is the world's largest iron-ore producer, and China is the biggest consumer and Vale's top customer.

Write to Rogerio Jelmayer at rogerio.jelmayer@wsj.com

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