Benchmark Asian iron ore futures fell on Friday and were on track for their second-biggest weekly loss so far this year, as moves in China to restrict steel mills' highly-pollutive operations and reduce production capacity weighed on sentiment.

The most-traded May iron ore on China's Dalian Commodity Exchange was down 0.3% at 1 059 yuan ($163.11) a tonne by 07:00 GMT, and has fallen 6% this week.

The front-month contract for the steelmaking ingredient on the Singapore Exchange dropped 3.2% to $159.35 a tonne and was poised to decline by 5% this week.

China's Ministry of Ecology and Environment has urged the country's top steelmaking city of Tangshan to crack down on violators of air quality rules after four mills had failed to implement production curbs during days of heavy pollution.

The Tangshan government issued a second-level pollution alert on March 8, urging heavy industrial companies such as steelmakers and coking plants to cut production accordingly.