By Andrius Sytas

VILNIUS (Reuters) - Estonia's Prime Minister Kaja Kallas faced pressure to resign on Friday after reports that her husband has part ownership of a company that has kept operations in Russia since Moscow invaded Ukraine.

Two major Estonian newspapers called on her to resign and two opinion polls found a majority of respondents thought she should step down. Kallas has said she does not believe her husband's companies have done anything wrong, while her husband said he was selling his stake in the company in question.

Kallas, who has urged European businesses to cut ties with Moscow, has been a leading critic of Russia in the European Union and NATO, and was considered by some to be a potential future secretary general of the military bloc.

Estonian public broadcaster ERR reported this week that Stark Logistics, an Estonian company in which Kallas' husband Arvo Hallik indirectly owns a 25% share, has been supplying an aerosol container factory in Russia, owned by another Estonian company.

It has earned 1.5 million euros from serving the factory since the beginning of the war, Estonian daily Eesti Paevaleht reported.

President Alar Karis and the leader of Social Democrats, the minority partner in Kallas' coalition government, called on Thursday on the prime minister to provide a detailed explanation.

Kallas told reporters on Thursday that while she did not have detailed knowledge of her husband's business, she was satisfied with his explanation that the company is only helping the other company while its Russian operations are wound down.

"What I am absolutely certain and confident about is that my husband's companies are not engaging in any immoral activity", Kallas was quoted by ERR as saying on Wednesday.

"They don't even buy fuel from Russia to avoid leaving a single euro or coin in Russia", she added.

Postimees, a major daily, said in an editorial on Friday that the prime minister had been evasive with her answers.

"We didn't get any answers on Wednesday or Thursday, and there is no reason to believe we will hear any on Saturday or Sunday. As a result, Postimees gives the prime minister the friendly advice that she start packing up today, to avoid leaving under even more shame, in the future", it said.

Eesti Paevaleht, the other major daily, suggested Kallas should hand in her resignation and then face a vote of confidence in parliament.

ERR reported that two opinion polls conducted by the Institute for Societal Studies/Nordstat and Turu-uuringute showed a 57% and 69% respectively of respondents thought Kallas should quit.

HUSBAND CUTS TIES WITH COMPANY

Kallas' husband announced on Friday he would sell his stake in the company and resign from its board of directors, ERR reported.

"We (the company) discussed the issue of transport for our client (in Russia) on several occasions, and we believed that we were doing the right thing, helping the right people and saving a good Estonian company, otherwise we could not have done it", ERR quoted Hallik as saying in a statement.

Kallas, who has lent sums of up to 350,000 euros to her husband's business, according to her statement published by BNS news wire, in December banned the Estonian state-owned railway company from transporting Russian nickel that does not fall under sanctions, saying it must not have any business dealings with Russia or Belarus.

Kallas' liberal Reform party, in power since 2021, won a general election in March, taking 37 seats in the 101-member parliament. She crafted a coalition with the liberal Estonia 200 party and the Social Democrat Party to command 60 votes.

(Reporting by Andrius Sytas in Vilnius; Editing by Frances Kerry)