Iran currently has 28.95 million barrels of oil and condensate in floating storage, a rise of 2.1 percent over the past week, the Fars news agency says.
Citing shipping data and sources which track tanker movements, the news agency said on Wednesday that 38 tankers with stored oil were parked in sea lanes close to terminals in four Iranian ports.
“Figures show 61 percent of the existing space for storage has been filled up,” Fars added.
Another report said India's oil imports from Iran fell 19 percent in November from a record high the previous month.
Shipments from Tehran were about 620,000 barrels per day (bpd) oil in November, down from 765,500 bpd in October, but well above 138,100 bpd in November 2016, Reuters said.
According to the report, Saudi Arabia and Iraq raised sales to the world's third biggest oil consumer, regaining their positions as the top two suppliers.
OPEC members and other global producers agreed at the end of last month to cut output in a bid to bolster weak oil prices, with Saudi Arabia pledging to bear the lion's share of reductions.
The rise in the kingdom’s exports to India is raising fresh questions about Riyadh's commitment to its pledge to cut output.
Supplies from Iran to India more than doubled in January-November to 468,900 bpd from 205,900 bpd in the same period last year, the data showed.
India's average Iranian oil imports in April-November rose 126 percent to 532,100 bpd and Tehran's share in overall purchases jumped to 12.5 percent from 5.9 percent, according to Reuters.
Since the lifting of sanctions in January, Iran has doubled oil exports as prices have recovered. Last month, the country was allowed by OPEC to raise output further while other members were obliged to slash.
Europe represents Iran's biggest post-sanctions recapture of the lost market, where the continent currently receives more than 700,000 barrels per day of Iranian crude oil.
'Eni clinches Italy's biggest oil deal in Iran'
On Wednesday, the Mehr news agency said Italy’s Eni had signed a contract to buy between 60,000 and 100,000 barrels per day of oil from Iran for one year.
The deal is the biggest sale of Iranian oil to Italy after Saras signed to take in 35,000-60,000 barrels per day of crude oil from the Middle Eastern producer earlier this year, the report said.
“Starting from January, 60,000 barrels at a minimum and a maximum of 100,000 barrels of oil is expected to be sold daily by the National Iranian Oil Company to Eni,” the news agency said.
“According to the terms of the agreement, 14.5 percent of the value of the exported oil will go to clearing the Italian company’s investment in phase 1 and 2 of the Darkhovin oil field,” Mehr added.