Japan's top construction machinery maker Komatsu said Tuesday its net profit dropped 30.2 percent in the first six months to September, citing weak demand in China and the yen's strength against the euro.

Komatsu's April-September net profit came to 66.1 billion yen ($831 million). Operating profit fell 16.3 percent to 111.3 billion yen on a 5.6 percent decline in sales to 930.8 billion yen.

"Sluggish demand for construction machinery in China and a drop in demand for products related to coal mines in Indonesia" led to a slide in sales, while the strong yen against the euro ate into profit, it said.

For the full year to March, Komatsu kept its forecasts at 157 billion yen net profit and 262 billion yen operating profit on 1.97 trillion yen sales.

Japanese manufacturers with exposure to China have been hit by a row over the sovereignty of a chain of islands in the East China Sea.

Shipments to China tumbled 14.1 percent in September on-year amid the dispute and a broader economic slowdown there.