The shares were off by as much as 3% in early trading, touching lows of €13.20, before paring losses. The stock is up by 2.4% in the year to date although it has under-performed many other oil group due to market concerns over whether or not it can restructure in order to cope with lower oil prices over the longer term.
The group swung to a quarterly loss of €290 million ($322.2 million), compared with expectations for net profit of €70 million.
Operating profit for the second quarter came in at €188 million, down 75% year on year and 59% below the consensus estimate of €460 million.
After factoring in special items, such as the write-off of deferred tax assets, the group swung to a reported loss of €446 million for the second quarter.
Operating profit from exploration and production came in at €355 million, down by 77% on the year and 28% below the consensus for profit of €490 million.
Gas and power, the group's second-largest revenue generator, swung to a quarterly loss of €229 million, a much deeper decline than the €77 million loss anticipated by the consensus.
But operating profit from the refining, marketing and the chemicals division came in at €156 million, about 290% ahead of the consensus estimate of €40 million.
Cash flows were €5.8 billion higher during the first half after the disposal of a 12.5% stake in subsidiary Saipem.
Eni said net debt ended the quarter at €13.8 billion after declining €3 billion in the first half.
Analysts at Bernstein said on Friday said Eni is on track with its upstream exploration and production restructuring, which entails reducing its exposure to low-margin production.
They reiterated their outperform recommendation on the stock.