KIEV, May 22 - A top Naftogaz Ukrayiny official resigned on Friday in the latest reshuffle as the national oil and gas company faces mounting financial challenges, a source at the company said.

Volodymyr Trykolych, a deputy head of Naftogaz Ukrayiny in charge of domestic gas supplies, resigned after a clash with the team of Prime Minister Yulia Tymoshenko, the source said.