China ramped up its buying of cheap Iranian crude last month after independent refiners were granted additional import quotas for 2021.

The nation imported almost 18 million barrels in November, equivalent to about 600,000 barrels a day, according to market intelligence firm Kpler. That’s up almost 40% from October and the biggest volume since August. Flows may be limited in the coming months, however, in part due to a broader crackdown on independent refiners and reduced demand resulting from virus restrictions.

China’s independent refiners, known as teapots, were set for a buying spree before the end of the year as they sought to use new import allocations they received in mid-October. That put Russian ESPO oil from the Far East, which usually takes less than a week to be shipped, and Iranian crude stored on ships off China and around Singapore and Malaysia in the spotlight.

The overall volume of crude and condensate stored at sea off key Asian regions fell to the lowest level since September as of Dec. 9, according to Kpler, which estimates that more than half of the oil in floating storage is from Iran and Venezuela. Traders say Iranian cargoes have been sold at a discount of at least $4 a barrel to the ICE Brent price.

The import figures from Kpler are at odds with official Chinese data, which indicate the nation hasn’t taken Iranian oil since December 2020. Supplies have often been re-branded as originating from Oman and Malaysia in the past.

Teapots have the flexibility to purchase cheap Iranian oil because many don’t have long-term deals with other Middle Eastern producers, unlike other Asian refiners. The independents buy cargoes via third parties that normally don’t own any assets in America, although China has opposed U.S. sanctions on Iran and accused Washington of reaching beyond its jurisdiction.

Still, relations are tense between the world’s two largest economies. Beijing this month threatened the U.S. with retaliation after Washington declared a diplomatic boycott of the Winter Olympics. The move is largely symbolic, considering the Covid-related restrictions officials would face in China.

The November spree likely marks the end of elevated buying for now. Flows are set to be subdued until late February following the Lunar New Year holiday and the Beijing Winter Olympics, which end on Feb. 20, according to Yuntao Liu, an oil analyst at Energy Aspects in London. China’s oil demand in early 2022 will have very limited upside, he added.

In the physical spot market, there are already signs of weakening for February loading cargoes. Spot premiums of ESPO crude—one of the grades favored by teapots—slipped to the lowest since August amid a crackdown on private refiners in China’s oil refining hub of Shandong province.