India, July 2 -- China has significantly tightened its restrictions on fertiliser export, slowing down imports into India and leading to a spurt in global prices, people familiar with the matter have said.

India relies on overseas markets to meet local demand of key crop nutrients, which are critical to food security in the world's most populous nation. Farmers in India are currently sowing a range of summer crops, which account for about half of the country's annual food supplies.

China is a large supplier of di-ammonium phosphate or DAP, the second-most widely used crop nutrient in India, whose imports have dwindled due to halting export clearances by China.

Signs of China's curbs first emerged last summer when global supplies of ure...