An alleged Ukrainian drone exploded at Russia’s Black Sea Fleet headquarters, spoiling its planned festivities dedicated to the Navy Crimean peninsula city of Sevastopol, a senior Russian official-annexed Crimea said on Sunday, July 31.

Aside from the at least five injured people, there were no reported casualties from the said bombing.

Sevastopol Governor Mikhail Razvozhaev reported the incident via Telegram, identifying that a “homemade drone” equipped with “low-powered” explosives flew into the courtyard of the fleet’s HQ on Sunday early morning. Furthermore, Crimean authorities raised the terrorism threat level for the region to “yellow,” the second-highest alert, and have canceled all activities for the celebration.

“There were no fatalities, six people were injured, two in moderate condition, the rest are in stable condition,” Razvozhaev stated.

As the Federal Security Service (FSB) investigated the situation, the governor advised residents to “remain calm and stay home if possible.”

The incident happened hours before Russian President Vladimir Putin was scheduled to attend the Navy Day celebrations in his hometown of St. Petersburg and approve Russia’s naval doctrine as Moscow presses on its military intervention in Ukraine, Reuters reported.

The Crimean peninsula, which included Sevastopol and the Black Sea mainland, was the first Ukrainian territory invaded and illegally annexed by Russian troops in 2014.