Iran's oil exports are set to rise more than a fifth in January and February from last year's daily average, data from a source with knowledge of its loading schedules shows, revealing how Tehran is ramping up sales after the lifting of sanctions.

The data is the first sign of a resurgence in crude shipments as the OPEC producer begins to raise output and clears out oil that has built up in offshore storage over the past four years of curtailed participation in world markets, Reuters reported.

The market is closely watching the pace of Iran's return to the market after sanctions were removed earlier this month, given a global glut in supplies that has pulled prices down 70 percent since mid-2014. Hopes that other top producers such as Saudi Arabia and Russia could cooperate with OPEC to contain production have lifted prices this week.

The Islamic Republic's overall exports will total around 1.44 million barrels a day (bpd) in February and about 1.5 million bpd in January, according to the data on Iran's preliminary tanker loading schedules.

Those shipping levels would be more than 20 percent higher than Iran's average daily exports last year, with the loadings this month at the highest since February 2014.

The increased shipments add to an oil surplus that analysts have estimated at around 1 million bpd. Official figures, based on oil arrival data from Iran's buyers, will not be available for January until mid-February and for February until mid-March.

"It was expected that Iran would increase their exports as quickly as possible," said Tony Nunan, a Mitsubishi Corp (8058.T) risk manager. "Physically they can do it because they have so much availability in floating storage."

Much of the nearly 40 million barrels of oil stored by Iran in domestic tankers is condensate – an ultra light grade of crude – shipping sources have said, and the faster the light crude is moved out the quicker the ships can be used for more oil deliveries.

Iran's shipments have surged nearly a quarter over the last four weeks from average tanker loadings of 1.21 million bpd last year following the lifting of sanctions earlier this month, according to the source's data.