The Vlast party, headed by the jailed former prime minister, reported the letter on its website on Saturday.

Foreign Ministry spokesman Vít Kolář confirmed to ČTK that Schwarzenberg sent the letter via the Czech representative in Kyiv. “The Minister would first like to congratulate Mrs. Tymoshenko on her birthday and wish her a speedy recovery,” Kolář said. According to him, apart from the letter, Tymoshenko also received flowers. The Czech Foreign Minister added that Europe has not forgotten the difficult situation Ukraine's opposition leader is experiencing.

Tymoshenko was also congratulated by the American ambassador in Kyiv, John Tefft, who condemned her mistreatment and expressed hope for her early release.

Last month, Tymoshenko was sentenced to seven years in prison for allegedly causing losses to the state when signing gas contracts with Russia. He has been in prison since August and, according to defense lawyers, the detention is seriously endangering his health.

He may suffer from problems with the circulatory system and complain of severe pain in his spine. The prison administration only sent him for a thorough examination last Wednesday after strong protests from the opposition and at the request of President Viktor Yanukovych.

Ukraine's prosecutor's office is investigating suspicions that a company once owned by current opposition leader Yulia Tymoshenko funded the murder-for-hire. According to the Prosecutor General's Office, it is possible that the transfer of money to the hitman's account was carried out by Tymošenko himself. This was stated on Kyiv TV by the First Deputy Prosecutor General of Ukraine, Renat Kuzmin.

According to Kuzmin, investigators are now working on the case of 1996, when influential businessman and member of the Ukrainian parliament Yevheny Shcherban was killed. The motive for the murder could have been Ščerbana's attempt to infiltrate the business practices of companies involved in the sale and distribution of natural gas in Ukraine. One of the owners of this company is Tymošenková.

Ščerban was shot dead by commando gunmen in March 1996 at Donetsk airport. Together with him, his wife and two crew members of Ščerbaň's private plane were murdered. Eight people were convicted of the murder, three of whom were sentenced to life in prison.

According to subsequent investigations, the politician's death was ordered by Pavlo Lazarenko, who was Prime Minister of Ukraine from June 1996 to July 1997.