Ukraine's Ambassador to the United States Valeriy Chaly has said there has been an increase in pranker attacks on Ukraine in the United States, and the location of their source is most likely in Moscow, the Ukrainian service of Voice of America has reported.

"I see the systematic work against the Ukrainian Embassy in the United States," Chaly said, adding that the attacks are organized in Moscow.

Chaly said several calls were made to three U.S. state governors and to two city mayors.

"It's impossible to do without gathering information... We know that there is serious preparation for such conversations and it is not just one person acting," he said.