Retail onion prices on Tuesday surged to Rs 73 per kg in Chennai -- the highest among the metro cities -- as supply disruption due to rains in producing areas have flared up bulb rates across the country, according to the Union Consumer Affairs Ministry data.

Onion prices ruled at Rs 51 per kg in Delhi, at Rs 65 per kg in Kolkata and at Rs 67 per kg in Mumbai on Tuesday, the data showed. Experts and traders are of the view that heavy rainfall in south and western regions has led to supply disruption and impacted the arrival of the kharif crop which will begin in full swing in the coming weeks. Currently, stored onion of rabi crop is being sold in the market.

Normally, prices come under pressure during this time in consuming areas but rains have created havoc in key producing areas, adding to supply woes, they said. South and west zones have seen a sharp rise in retail onion prices, according to the ministry's data.

In Chennai, onion prices rose sharply to Rs 73 per kg as against Rs 33 per kg in the year-ago period. Whereas in Mumbai, rates rose to Rs 67 per kg from Rs 56 per kg, while that in Kolkata to Rs 65 per kg from 60 per kg. In Delhi prices increased to Rs 51 per kg from Rs 46 per kg in the year-ago period.

For instance in Nashik in Maharashtra, the country''s top onion producing state, retail prices skyrocketed to Rs 66 per kg on Tuesday from Rs 35 per kg in the year-ago period. To improve domestic availability and check prices, the government last month banned export of onions.