Royal Dutch Shell's profits have fallen 32% after it was hit by weaker refining margins and the worsening security situation in Nigeria.
The oil giant also blamed rising costs as it posted underlying profits of 4.5 billion US dollars (£2.8 billion) for the quarter to September 30.
Shares fell by more than 4% today as Shell's results failed to match the forecast-beating performance of rival BP earlier this week.
The ongoing challenges in Nigeria, where oil theft and disruption to gas supplies is causing widespread environmental damage, impacted on Shell's production volumes in the quarter.
Chief executive Peter Voser, who is leaving the company at the end of this year, said: "We are facing headwinds from weak industry refining margins, and the security situation in Nigeria, which continue to erode the near term outlook."
However he said the company's flow of projects for 2014 and beyond was strong, following the opening of a series of new oil and gas fields in the last few months, including in Iraq.
He added: "Shell's sustained investment in new growth projects will drive our financial performance."
The biggest factor in the third quarter decline was the company's downstream operation, where profits fell 49% to 892 million US dollars (£556.2 million) as a result of weaker refining conditions caused by industry overcapacity and weak demand.
Investec Securities analyst Neill Morton said Shell's "sizeable" earnings miss, plus higher guidance on capital spending and uncertainty over its disposal plans had unnerved investors.
He added: " The numbers are not quite as disappointing as they first appear , but arguably still raise question marks over Shell's communication with the market."
Shell said it had distributed 11 billion US dollars (£6.9 billion) of dividends in the last 12 months, while it is on track to make up to 5 billion US dollars (£3.1 billion) of share buy backs.
Mr Voser added: "Our cash flow pays for Shell's dividends and investment in new projects to ensure affordable and reliable energy supplies for our customers, and to add value for our shareholders."