An armed man in military fatigues stands guard outside a regional administration building seized by the separatists in the eastern Ukrainian city of Slovyansk on April 23.
Ukraine's government says it has formally ended an Easter truce and is preparing a fresh military offensive against pro-Russian insurgents in the east following the killing of a local politician.
First Deputy Prime Minister Vitaliy Yarema said on April 23 that Kyiv was poised to relaunch the "active phase" of its "antiterrorist operation" against separatists occupying government buildings in a dozen towns in Ukraine's Russian-leaning east.
In Moscow, Foreign Minister Sergei Lavrov said Russia will retaliate if ethnic Russians in eastern Ukraine are threatened.
Speaking to the state-controlled RT channel on April 23, he said, "If we are attacked, we would certainly respond."
He rejected criticism of Moscow's decision to deploy tens of thousands of troops to Ukraine's eastern border, saying the troops remain on Russian territory and have not crossed into Ukraine.
Lavrov also accused the United States of "running the show" in Ukraine, pointing out that Kyiv's announced resumption of its offensive in the east coincided with a visit by U.S. Vice President Joe Biden.
On April 22, acting Ukrainian President Oleksandr Turchynov ordered a fresh push to dislodge insurgents following the discovery of two "brutally tortured" bodies near the rebel-held city of Slovyansk.
The Interior Ministry on April 23 formally identified one of the two victims as Volodymyr Rybak, a local politician from Turchynov's Batkivshchyna (Fatherland) party, who was believed to have been kidnapped last week.. The name of the second victim has not been released.
The Interior Ministry said both men had been tortured and drowned while still alive.
Turchynov blamed the rebels for the killings, which he said were "carried out with the full support and indulgence" of Russia.
A video has emerged showing Rybak being mobbed by a pro-Russian crowd shortly before disappearing.
In the footage, published by the local news site Gorlovka.ua, Rybak is insulted and manhandled by several men, including a masked man in camouflage, after trying to remove the flag of the separatist "Donetsk Republic" from the building.
The Interior Ministry said he was seen being bundled into a car by masked men in camouflage later that day.
WATCH: U.S. Representative Ed Royce, the chairman of the House Foreign Affairs Committee, says Russia needs to take action to enforce a recent international agreement to de-escalate tensions in Ukraine. (RFE/RL's Ukrainian Service)
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In Kyiv, U.S. Congressman Urges Russia To Implement Ukraine Agreement
Meanwhile, insurgents in eastern Ukraine acknowledged on April 23 that they are holding American Simon Ostrovsky, a journalist for Vice News.
Stella Khorosheva, a spokeswoman for the pro-Russian rebels in the eastern city of Slovyansk, said Ostrovsky was being held for unspecified "bad activities." She said he was "fine" and that insurgents were holding him pending their own investigation.
In a statement, Vice News said it "is in contact with the U.S. State Department and other appropriate government authorities to secure the safety and security" of Ostrovsky.
With reporting by Reuters, AFP, AP, Interfax, and RT
