(Adds details, analyst comment)
WARSAW, Feb 16 (Reuters) - State-run Polish gas company PGNiG estimated on Thursday it made a fourth-quarter net profit of 690 million zlotys ($170 million), recovering from a 21 million loss in the same period a year earlier when it was hit by impairments.
The forecast, released unexpectedly two weeks before scheduled results for 2016, was higher than some analysts had expected and sent the company's shares to their highest since November 2015.
"Looking at the business segments, the trade and storage is a big, positive surprise, but it is difficult to say now what it was caused by," said Vestor DM analyst Beata Szparaga.
At 1005 GMT, PGNiG shares were up 8 percent to 6.12 zlotys.
PGNiG said net profit excluding impairments, according to preliminary estimates, came to 830 million zlotys, while revenues rose to 10 billion zlotys from 9.77 billion a year earlier.
It estimated fourth-quarter earnings before interest, tax, depreciation and amortisation (EBITDA) at 1.69 billion zlotys.
PGNiG, which postponed the release of full 2016 results to March 8 from March 3, said net profit for the whole of the year was estimated at 2.32 billion zlotys.
$1 = 4.0688 zlotys Reporting by Lidia Kelly and Anna Wlodarczak-Semczuk; Writing by Agnieszka Barteczko; Editing by Mark Potter