Opec crude oil output rose in February, the first monthly increase since October, due to higher exports from Iraq and a slight increase in supply from top exporter Saudi Arabia, said a survey.

Supply from the 12-member Organisation of the Petroleum Exporting Countries was 30.32 million barrels per day (bpd), up from 30.21m bpd in January, the survey of shipping data and sources at oil firms, Opec and consultants found.

The survey indicates Opec output has risen for the first month since October 2012, before cutbacks by Saudi Arabia which coincided with a rise in oil prices towards $120 a barrel. Even so, analysts said, supply remains low compared to recent months.

"It is a very moderate rise. All in all, the production level remains close to multi-month lows," said Carsten Fritsch, analyst at Commerzbank in Frankfurt.

January's revised output was the lowest since October 2011, according to surveys. In February, Opec pumped just 320,000 bpd more than its supply target of 30m bpd - a lower level of overproduction than during any month of 2012.

With oil prices above Saudi Arabia's preferred $100 a barrel but with expectations of slower demand in early 2013, Opec left its output target unchanged at a meeting in December, leaving the door open to informal supply tweaks depending on demand.

Saudi Arabia boosted supply to market by 100,000 bpd in February according to the survey, to 9.2m bpd. It had cut output sharply in the last two months of 2012, and again in January.

No sizeable increase is expected until the second quarter, when growth in Asia and a seasonally higher need for crude in domestic power plants are likely to lead to higher Saudi output, sources said.

Iraq, the world's fastest-growing exporter, also increased supply. But exports of Kirkuk crude were restrained by the dispute between the central government and the Kurdistan region over payments, and bad weather and maintenance kept a lid on southern exports.

There were supply decreases in Iran and Nigeria last month, the survey found.

Iran's crude exports fell in January to around 1.1m bpd from a post-sanctions high of at least 1.4m bpd in the previous month, analysts and shipping sources said.

Exports slipped further in February, sources in the survey said. Iranian output in coming months will face increasing headwinds from the implementation of new sanctions on Wednesday by the US.

"Judging by what's going on in the market and with the sanctions, you would think it is trending downwards," said one of the sources, a consultant who also declined to be identified.

Crude output remained under pressure in Libya, where oil installations have become a focal point of protests. The operator of Libya's largest refinery, Ras Lanuf, declared a force majeure until March 7.

Output in Nigeria, disrupted in the last few months by oil spills, flooding and theft, also edged lower. Exxon Mobil on February 7 declared force majeure on exports of Nigeria's largest crude stream, Qua Iboe, due to pipeline repair work.

The measure was lifted on February 22, although oil traders said some exports had been delayed into March from February.-Reuters