British prosecutors named two Russian men — believed to be officers in Russia's intelligence service — they believe were behind the nerve agent attack on a former Russian spy and his daughter in the U.K. earlier this year.

They named the men as Alexander Petrov and Ruslan Boshirov, and said they are officers in Russia's foreign military intelligence agency, the GRU.

They have been charged with the attempted murder of Sergei Skripal and his daughter Yulia, who were found unconscious on a park bench in the small English city of Salisbury in March.

Following the announcement, Prime Minister Theresa May reiterated the U.K.'s allegation that the Russian state had orchestrated the attack on the former Russian spy, who had become a double-agent for the U.K.'s intelligence services in the 1990s and early 2000s — a factor seen as motivation for the attack.

Speaking to parliament Wednesday, May said the U.K.'s security and intelligence agencies had determined that the men were officers belonging to the GRU.

"Based on a body of evidence, the government has concluded that the two individuals named ... are officers from the Russian military intelligence service, also known as the GRU. The GRU is a highly disciplined organization with an established chain of command so this was not a rogue operation," she said. "It was almost certainly approved outside the GRU at a senior level of the Russian state."