Asia's naphtha physical crack plunged more than 100% to return to the negative zone for the first time since April as inflating supplies weighed.

The crack value sank to a discount of $1.50 a tonne to Brent crude versus a premium of $11.13 from the previous day.

East-bound cargoes to Asia next month are seen high despite sellers already grappling with some historical high volume of 2.9 million tonnes of cargoes arriving this month from the West including Europe, Mediterranean and the United States.

The weak gasoline fundamentals, where more than 280,000 tonnes of petrol were floating off Singapore/Malaysia and many more cargoes stored in ships in various parts of the globe, were also dragging down the naphtha cracks, an industry source said.

Naphtha is used as a feedstock for petrochemicals as well as a component for gasoline production/blending.

Formosa, Asia's top naphtha importer, was out to buy the fuel in a tender expected to be awarded late this week.

The purchase tender came in the same week where South Korea's YNCC and KPIC and Malaysia-based Titan had picked up cargoes for second-half June delivery..

Asia's gasoline crack was at a discount of $1.70 a barrel to Brent crude as heavy supplies have kept the crack at discount value since March 16.

Although gasoline stockpiles in Singapore were lower week-on-week, the levels were higher versus the same period last year.

Based on data from Enterprise Singapore, onshore light distillates stockpiles for the week ended Wednesday was at a five-week low of 15.3 million barrels but this was nearly 38% higher than the same week last year.