(Bloomberg) — Oil options show investors are betting prices will rise further as escalating hostilities between Israel and Iran raise the risk that energy infrastructure or crude tankers will be targeted.

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Call options, which profit when prices rise, were at a premium to puts at Wednesday’s close for the first time since mid-August. The options skew became more bullish in Asia on Thursday, although trading was relatively thin due to a weeklong holiday in China.

The options action is corresponding with a rise in futures on the prospect of a full-blown war in the Middle East that could disrupt oil production and transport. Brent is up about 4% since Iran fired more than 100 ballistic missiles at Israel earlier this week, and a gauge of implied volatility for the global benchmark has jumped to the highest level in almost a year.

Aggregate traded volumes of call options for Brent also spiked, with more than 372,000 of the contracts changing hands on Wednesday. That compares with an average of about 129,000 over September. Higher-than-average volumes of WTI calls were also traded.

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