Ukraine's Interior Ministry has sent a summons to Ukrainian businessman Dmytro Firtash for questioning and carrying out investigative actions, Interior Minister Arsen Avakov has said.

"In connection with the investigation into the criminal case on Ostchem Group's corruption schemes and the theft of the state property of Ukraine, the investigative department of the Ukrainian Interior Ministry sent a summons to Dmytro Firtash for questioning and carrying out investigative actions," Avakov wrote on his Facebook page.

According to the minister, the authority has appealed to the United Stated FBI with an invitation to participate in joint investigative actions on the case.

"Given the materials on the damages to the state of Ukraine available to the investigators of the two countries, the Interior Ministry is ready to carry out joint investigative actions on the case both in the territory of Ukraine and in the United States," the minister said.

As reported, Prime Minister of Ukraine Arseniy Yatseniuk on April 30 said the Interior Ministry had opened criminal proceedings on the fact of conspiracy by the employees of Naftogaz Ukrainy and Ostchem, which resulted in the damage of UAH 5.7 billion to the state.