Libyan rebels aligned with Tripoli-based government attacks oil facilities.
Naimi directed Opec's 2014 decision to fight for market share, instead of cutting output to support prices.
Igor Sechin said some countries are pursuing their personal interests and undermining other members within the oil cartel.
No change expected in Saudi oil policy following death of King Abdullah bin Abdulaziz al-Saud.
Prince Alwaleed bin Talal defends Saudi decision not to cut production to boost prices.
Crude oil prices have ended down for the past seven consecutive weeks on oversupply concerns.
Suhail bin Mohammed al-Mazrouei says crude prices could recover if non-Opec producers "act rationally".
US crude output at record level as Saudi Aramco adopts dual pricing strategy
In 2013 and 2012 oil prices averaged $100/bbl.
China's manufacturing PMI fell below 50, increasing global demand worries.
Analysts say Brent crude could drop to $55 a barrel early next year.
In the budget announced for the next year, spending has been pegged at 860bn riyals and revenue generation at 715bn riyals.
Oil price collapse is sensational news for OECD policymakers but not Russia and OPEC.
Opec producers banking on slowdown in US shale boom and rising demand fuelled by low prices.
Saudi Arabian Oil Minister Ali al-Naimi said Opec won't cut production regardless of the price.
Brent crude oil could bottom-out at $40 before recovering slightly as US shale production drops.
Opec has controlled the global oil market and has set oil prices for almost half a century until now.
Brent crude fell to its lowest level since 2009 as Opec producers seek to protect market share.
Oil firms are set to reduce capital expenditure due to slide in oil prices.
Brent oil has fallen below $60 a barrel for the first time since 2009.
At least 15% of US shale producers are losing money at current prices, and more than half will be under water if US crude falls below $55, says BoA.
Crude prices fall to around $68 a barrel on Monday.