Senior security official: Anti-terror operation suspended as Russian troops amass on border (LIVE UPDATES, VIDEO)

Editor's Note: On April 22, interim President Oleksandr Turchynov announced that Ukraine would restart its anti-terror operation to quell Russian-backed separatist movements in Donetsk Oblast. The operation had been put on hold after quadrilateral talks between the U.S., EU, Russia, and Ukraine in Geneva led to an agreement whereby separatists in eastern Ukraine were requested vacate public spaces and buildings, and surrender their arms. The insurgents refused to comply with the stipulations of the Geneva Statement, and, over Easter weekend, seized several more buildings in Donetsk Oblast.

On the morning of April 24, Ukrainian troops repelled a separatist attack on a military base in the city of Artemivsk, Donetsk Oblast. Ukrainian forces also retook the city council building in the city of Mariupol, Donetsk Oblast, which had been controlled by insurgents since April 13.

On April 23, Russian Foreign Minister Sergei Lavrov said in an interview with Russia Today that Russia will be forced to protect ethnic Russians in Ukraine if they are attacked directly.

The Kyiv Post will be live blogging the anti-terrorist operation as it continues in eastern Ukraine.

Video: Russian tanks, APCs, trucks mobilizing 10 kilometers from eastern border

4:15 – Citizen journalists purportedly located in Novoshakhtinsk, a Russian city 10 kilometers from Ukraine's eastern border in Rostov Oblast, shot footage of Russian military mobilizing. Columns of armored personnel carriers, artillery weapons, tanks and trucks, presumably transporting Russian soldiers are seen driving in the city's main highway. – Mark Rachkevych

Anti-terror operation temporarily halted, government reformulating plan

16:00 p.m. – The original plan for Sloviansk today was to recapture the town from separatists, including all government buildings they had taken over, a senior security official told the Kyiv Post. The operation, however, has been halted for the moment as the government is reformulating the plan based on their latest intelligence from the eastern border, the official said.

According to Ukrainian intelligence, the risk of Russian troops crossing the border has increased dramatically, according to a senior security official in the government. The government also confirms that there are seven people dead as a result of the operation. "The separatists are panicking," the official said.

Meanwhile, AFP and Russia Today, citing the Russian defense ministry, report that Moscow has ordered new military exercises to be conducted on its border with Ukraine. -- Katya Gorchinskaya, Christopher J. Miller

Civil war has started, says leader of Donetsk People's Republic 

15:10 p.m. – According to Interfax Ukraine, the leaders of the Donetsk People's Republic have announced a general mobilization of separatist forces in eastern Ukraine in response to the anti-terror operation that Ukrainian authorities launched outside the city of Sloviansk on April 24. 

The leadership of the self-proclaimed republic told Interfax that "a combined arms operation has been launched in Sloviansk. This means only one thing: a civil war." -- Isaac Webb 

UKRAINE, Slavyansk: Ukrainian special forces take position at an abandoned roadblock in the eastern Ukrainian city of Slavyansk on April 24, 2014. Ukraine's military launched an assault on the flashpoint rebel-held town of Slavyansk, sending in armoured vehicles and a helicopter, AFP journalists in the town reported. Several armoured personnel carriers drove past an abandoned rebel roadblock in flames to take up position at the entry to the town. AFP PHOTO/KIRILL KUDRYAVTSEV

SBU releases Russian military chatter over killing of Horlivka lawmaker (VIDEO)

2:30 p.m. – Ukraine’s Security Service (SBU) has released a YouTube video it says implicates high-ranking Russian Military Intelligence officers in the April 17 abduction and subsequent killing of Horlivka City Councilman Volodymyr Rybak.

Rybak that day tried raising the Ukrainian national flag atop the local legislature building. His dead body was found in a river near Sloviansk – 65 kilometers from Horlivka – on April 19, along with an unidentified corpse. An Interior Ministry criminal investigator said his body had signs of torture and his belly was ripped open.

The first part of the video allegedly shows a recording of Russian Military Intelligence Lieutenant Colonel Igor Bezlier ordering a subordinate to abduct Rybak, tie his hands and blindfold him while driving him away to a remote place so that he could rendezvous with the captors.

In the second part of the recording, Russian Military Intelligence Colonel Igor Strelkov – who the SBU says is coordinating the Kremlin-backed separatist movement in eastern Ukraine – calls Vyacheslav Ponomaryov, the self-proclaimed mayor of Sloviansk, “to come and pick up (Rybak’s) body because it is starting to stink.”

In response, Ponomaryov complies, and says he will come to take and “bury the punk.” – Mark Rachkevych

Putin calls Ukraine's anti-terror operation "a serious crime against its people" 

Speaking at a Media Forum in St. Petersburg on Thursday, Russian President Vladimir Putin said that "If today's regime in Kiev has actually begun using its army against civilians within the country, then that, without a doubt, is a serious crime against its people," according to Voice of Russia, a Russian state-controlled news website.

He said that the use of force against Ukrainians is "very serious" and will have "consequences." -- Isaac Webb 

Interior Ministry urges people in Sloviansk not to leave their homes

1:40 p.m. -- The Ukrainian Interior Ministry has released a statement telling people in the beseiged city of Sloviansk not to leave their homes as the military's anti-terror operation continues in northern Donetsk Oblast.

The statement requests that parents "do not let unattended children in the streets," and encourages citizens "not to succumb to provocations and not to carry out the criminal orders of representatives of the self-proclaimed government."

Ukrainian forces distributed leaflets to residents of Sloviansk encouraging them to remain peaceful.

The Ministry has reported on its website that the "self-proclaimed mayor of Sloviansk Ponomarev" announced that anyone seen with the leaflet will be "shot on the spot." -- Isaac Webb 

Five killed, one wounded as Ukrainian troops descend on Sloviansk

1:16 p.m. -- Ukrainian troops have taken control of three checkpoints surrounding the city of Sloviansk in northern Donetsk Oblast. 

According to the Ukrainian Interior Ministry, five insurgents have been killed and one police officer has been wounded in the attack.

In the video below, a Ukrainian tank passes through a checkpoint on the road to Sloviansk.

The barricades at the checkpoints have been set on fire, and large plumes of smoke can be seen billowing over the city. 

In this video, Ukrainian troops are seen at a checkpoint:

Ukrainian helicopters have been spotted flying over the city. 

The Interior Ministry is requesting that people do not leave their homes. -- Isaac Webb