Sri Lanka usually imports 4,000-5,000 tonnes of big onions a week from India.
The Pettah Wholesale Traders' Association vice chairman Nihal Seneviratne said stocks of 'big' onions, previously known as 'Bombay onions', had run out by Thursday.
India on Monday suspended exports of onions, a key food staple, after prices of the vegetable soared, adding to the government's inflation woes.
Seneviratne said traders in Sri Lanka's main wholesale market in the capital Colombo had enough stocks of the smaller 'red onions' grown locally in northern Jaffna and north-western Puttalam.
"There are enough stocks of red onions from Puttalam and Jaffna. There is only one local harvest a year - the three months from August to October.
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Traders had placed orders for big onions from Pakistan and the first shipment is expected on Monday and the second ship by Friday, Seneviratne said.
"Then there will be no shortage of big onions but prices will go up.
Prices of imported onion have gone up because