Opec's petroleum exports jumped in value by almost 10 percent in 2012 year-on-year and the producers' GDP climbed 12 percent, according to the group's latest report, an income surge that looks harder to repeat this year.

The gains, announced in Opec's Annual Statistical Bulletin 2013 on Monday, reflect record prices and steadily climbing output last year from many members of the Organization of the Petroleum Exporting Countries.

An increase in cash flow is a big advantage for producer countries as they face pressures including rising populations, infrastructure investment and increased social spending to head off Arab Spring-type protests.

The value of the group's petroleum exports rose to $1.26 trillion in 2012 from $1.15 trillion in 2011, the report said, while its collective GDP at current prices amounted to $3.35 trillion, up from $3.0 trillion in 2011.

Opec said petroleum exports also included refined oil products when applicable, as well as crude.

Libya posted Opec's biggest increase in exports as its oil industry recovered after the 2011 civil war, earning petroleum export revenues of $60.2 billion, up from $18.6 billion in 2011.

The largest fall was in Iran, reflecting the drop in its oil exports last year because of tighter U.S. and European sanctions over its nuclear programme. Iran's petroleum exports declined to $101 billion from $115 billion in 2011.

In 2012, Brent crude averaged $111.70 a barrel, a record high. Analysts in a Reuters poll expect it to average around $106 this year, while Opec's production overall has declined, suggesting revenue will struggle to beat 2012's total in 2013.

Opec's proven oil reserves, meanwhile, were little changed in 2012, according to the report. Reserves grew by 0.2 percent to 1.2 trillion barrels and Venezuela remained the biggest reserves holder.

The reserves figures are regarded with skepticism by some analysts, who cite competitive upgrades among members and no change in the reserves figures reported by some countries for a number of years. – Reuters