Lotos, Poland's second-largest refiner, recorded a second-quarter net loss of zł.649 million as a weakened zloty increased the payments the group had to make on foreign-currency denominated loans.

A year earlier the Gdańsk-based refiner turned a net profit of zł.745 million.

Losses from financial operations totaled zł.1.05 billion, generated largely after a revaluation of the group's dollar debt. The złoty weakened by some 15 percent in Q2.

Lotos took on the debt to finance an increase in its throughput capacity to over 10 million metric tons of oil a year in 2011 – up from six million tons in 2009.

Despite its disappointing bottom line, the rising price of crude and a favorable Brent-Ural differential helped the group to improve results from its core operations. Revenues increased 38 percent to zł.4.75 billion, while operating profit stood at zł.230 million, up from zł.158 million a year earlier.