Onion prices in Tamil Nadu's capital city Chennai have doubled in a week. With onion supply in the city dwindling, a kilo of the vegetable now costs around Rs. 75-80 across the city from last week's Rs. 40-45. Shopkeepers have blamed Maharashtra's Nashik for dwindling supply. Nashik is the key hub from where Chennai procures a significant share of its onions. Onion prices across the country had shot up last month after the centre banned the vegetable's exports after increasing rain delayed harvests.