By Chris Borowski

WARSAW (Reuters) - Polish prosecutors denied a newspaper report that investigators found traces of explosives on the wreckage of the government jet that crashed in Russia two years ago, killing Poland's President Lech Kaczynski and 95 others.

Rzeczpospolita daily said on Tuesday that Polish investigators who examined the remains of the plane in Russia found signs of TNT and nitro-glycerine on the wings and in the cabin, including on 30 seats.

The report strengthened accusations by rightists groups that investigators ignored evidence of outside involvement and prompted opposition leader Jaroslaw Kaczynski, the twin brother of Lech, to call for the government to resign.

But Polish military prosecutors said they were sticking to their finding that the crash was not an assassination and no explosives were found on the remains of the government Tu-154 that crashed during its approach to a small airport near the Russian city of Smolensk on April 10, 2010.

"It is not true that investigators found traces of TNT or nitro-glycerine," said Colonel Ireneusz Szelag from the military prosecutors' office.

"Evidence and opinions collected so far have in no way provided support to the belief that the crash was a result of actions by third parties, that is to say an assassination," he told a news conference.

Russian investigators had blamed the Polish crew for trying to land in heavy fog, while their Polish counterparts also said the airport controllers should not have allowed the plane to attempt an approach.

Moscow and Warsaw have faced renewed criticism over their handling of the Smolensk investigation after Polish prosecutors admitted last month that families of two of the victims received and buried the wrong remains.

On Tuesday, Szelag said two more bodies were misidentified and lawyers for families of other victims feared more remains may need to be exhumed.

Before the denial by prosecutors, Jaroslaw Kaczynski said the newspaper report was proof that his twin brother and the other passengers of the presidential plane were murdered.

"We demand the resignation of the government of (Prime Minister) Donald Tusk," Kaczynski told reporters. "It cannot be that Poland is governed by people who have obfuscated for 30 months in the matter of what we can now say is a heinous crime."

(Reporting by Chris Borowski; Editing by Jon Hemming)