Ukraine's government Saturday has resumed military operations to suppress the pro-Russian separatists, who have taken control of several buildings in the port city of Odessa, even as the U.S. is condemning the violence that took place in the city on Friday.

Arsen Avakov, Ukraine's interior minister, said Saturday that his government has resumed operations near the eastern city of Kramatorsk, following the fire that had engulfed a building in Odessa, which was taken over by pro-Moscow supporters, that killed more than 31 people Friday. According to Reuters, nearly 130 people were detained after the conflict that took place in Odessa, along with protesters fighting on the streets.

"The events in Odessa that led to the deadly fire in the trade union building dramatically underscore the need for an immediate de-escalation of tensions in Ukraine. The violence and efforts to destabilize the country must end. We again call for the immediate implementation of the commitments made in Geneva on April 17," the U.S. Department of State said in a statement on Friday.

Petro Lutsiuk, the local police chief, said that those detained could face charges of taking part in riots and premeditated murder for Friday's violence, Reuters reported.

"The situation remains under control, but the security situation is threatened by Russian special agents," Danylo Lubkivsky, Ukraine's deputy foreign minister said, according to the BBC, adding: "That's why we are requesting and demanding Russian authorities to stop their efforts that can undermine regional security and stability."

Despite Ukraine and the U.S. alleging that Moscow is supporting the protesters in the eastern part of Ukraine, Russia's President Vladimir Putin had warned Kiev before taking any action against the protesters.

"While Russia is making efforts to de-escalate and settle the conflict, the Kiev regime has turned to firing on civilian towns with military aircraft and has begun a punitive operation, effectively destroying the last hope of survival for the Geneva accords," Dmitry Peskov, Putin's spokesperson, said, according to Reuters.