Spotlight: Ukraine on high alert as Russia raps Kiev for provocation in Crimea

Ukraine has put its forces near Crimea and in eastern Ukraine on high alert, as Russia accused it of provocation in Crimea and vowed to take additional measures.

Ukrainian President Petro Poroshenko said on Thursday that he has ordered the country's defense and law enforcement agencies to put their units near Crimea and in eastern Ukraine on high alert.

"I gave the instructions to boost combat readiness of all units deployed in the areas near the administrative border with the autonomous republic of Crimea and on the entire contact line in the Donbas," Poroshenko said on Twitter after meeting the leadership of the country's defense and law enforcement agencies and the Foreign Ministry.

Later Thursday, Ukrainian State Border Service's Spokesman Oleg Slobodyan said that Ukraine's frontier guards have already started enhancing the combat readiness of their units near Crimea and in Lugansk and Donetsk regions.

"First of all, this means mobilization of reserves and checks of our interactions with the Ukrainian armed forces and other defence and law enforcement agencies," Slobodyan was quoted as saying by Interfax-Ukraine news agency.

The Ukrainian move came amid an escalation of tensions between Ukraine and Russia, which flared on Wednesday after Moscow accused Kiev of plotting terrorist attacks in Crimea and vowed to take additional measures to ensure the safety of infrastructure and citizens there.

Ukraine dismissed the claim, terming the allegations as Moscow's attempt to justify its alleged re-deployment of troops and actions in the region.

Crimea, which was previously part of Ukraine, was incorporated into Russia in 2014 following a referendum, which was recognized by Moscow but rejected by Ukraine and Western powers.

In eastern Ukraine, the fighting between government troops and independence-seeking insurgents has been underway since April 2014.

Ukraine, the United States and European countries have long accused Russia of arming and encouraging insurgents in eastern Ukraine, but Russia has denied the charges.

Russia's Federal Security Service said Wednesday it had dismantled a spy ring in Crimea organized by the Ukrainian Defense Ministry, which it said was plotting acts of terror and sabotage on critical and life-supporting elements of the peninsula's infrastructure.

The Russian Foreign Ministry also said on Thursday that such acts undermined the preparation for local elections and the political stability.

"Russia is seriously concerned about the inaction of Kiev authorities in the face of growing militant rhetoric and violent actions taken and planned by the so-called volunteer battalions and other extremists," the ministry said in a statement.

The ministry called on the Ukrainian government to stop provocations and fully fulfil its commitments to the Minsk agreements aimed at a peaceful settlement of the Ukraine crisis.

Russia would do its utmost to protect Crimea's stability and security, while Kiev and its foreign supporters would suffer the consequences if any damage were inflicted on the Russian side, the ministry said.

Later Thursday, a court in Crimea announced that a Ukrainian suspect in the terrorist plot, Yevgeny Panov, was arrested.

Also on Thursday, the United States expressed concern over the increased tension "near the administrative boundary between Crimea and Ukraine," urging Russia and Ukraine to avoid the escalation of tension in Crimea. Endi