Ukraine officially denied on Monday sending "saboteurs" to Russia, after Moscow said it had killed five of them on its soil, a declaration that threatens to escalate the already simmering tensions between the two neighboring countries, while the mutual bombardment continues between Ukrainian forces and Russian-backed militants in the Donbass region.

"None of our soldiers crossed the border with Russia, and none of them were killed today," Anton Gerashchenko, a senior Ukrainian interior ministry official, told reporters.

The Russian Security Service stated that a Ukrainian shell targeted a Russian checkpoint in the city of Rostov on the border between the two countries, while the Ukrainian army denied responsibility for launching it.


The Russian security service had stated that the bombing of the Ukrainian side had hit and destroyed a border guard post inside Russian territory, 150 meters away from the border with Ukraine. It did not mention any casualties as a result of the bombing.

The Ukrainian army announced that it had recorded 32 violations by the militants in Donbass since Monday morning.

Al-Jazeera correspondent spoke about the injury of 3 Ukrainian soldiers as a result of the bombing of their positions in the region.

The Ukrainian army accused the separatists of placing their heavy military equipment in populated areas and near residential buildings;

He denied targeting infrastructure.

Al-Jazeera correspondent said that heavy artillery shelling was heard in the vicinity of Donetsk Airport and the western neighborhoods of the city.


Civilian victims

For their part, the "separatists" in eastern Ukraine announced that there were civilian and military casualties as a result of the continuous and violent bombardment by the Ukrainian forces;

They noted that residential areas were targeted nine times with 120-mm mortars, prohibited under the Minsk agreements.

The "separatists" spoke of the killing of one of their soldiers and two civilians, and the injury of three, in Ukrainian shelling of towns.

The so-called "people's militia" in Lugansk said that Ukrainian shells fell on two schools and a number of houses on the outskirts of the city;

It explained that its forces responded to the sources of fire along the line of contact;

It also indicated that more than 400 volunteers from Russia joined its forces.

The separatists in Donetsk said that a Ukrainian military group penetrated this morning their fortifications and blew up a weapons and ammunition depot in the "Novo-Azovsk" region, south of Donetsk.


The separatists added that the attack led to the detonation of the entire warehouse, and that those forces were seeking to open a corridor towards the Russian border;

This prompted their forces to close roads and stop traffic in the area.

Russian Defense Minister Sergei Shoigu said about 60,000 Ukrainian soldiers are stationed near the Lugansk and Donetsk borders.

He explained that Kiev's declaration of its desire to return to being a nuclear power is very dangerous, stressing that Ukraine has the potential to manufacture nuclear weapons greater than Iran and North Korea.

Shoigu told President Putin on Monday that Ukraine had amassed a lot of forces near the "separatist" areas in the east of the country and might be preparing to try to retake them by force, something Kiev has repeatedly denied.

Shoigu accused Ukraine of intensifying its bombing of these areas.

Pro-Russian militants in Donetsk and Luhansk called on Putin to recognize the "independence" of the two regions and sign a cooperation agreement.

Putin confirmed that Russia is studying the request and will decide on it today.


escalation

For its part, the US Department of Defense (Pentagon) said that it expects significant losses on the ground in Ukraine if the invasion occurs, as well as losses among the Russians.

The Pentagon added that it is still witnessing the build-up of large combat forces on the border with Ukraine, noting that if Putin chooses to go to Ukraine with large forces, the result will be bloody.

The Pentagon said diplomacy was still possible, although time was running out.

Three Western officials said Western fears of a Russian invasion of Ukraine had increased in the past few days, and that the outlook appeared to be bleak.

The officials, who spoke on condition of anonymity, added that Russian military units were preparing to invade Ukraine, and that there was an escalation over what were believed to be provocations in two Russian-backed separatist regions of Ukraine.

Officials stressed that the overall picture was "very bleak, with storm clouds accumulating on the Ukrainian border."


Invitation to leave

At the same time, the US Embassy in Moscow called on its citizens to prepare personal insurance and evacuation plans, not dependent on the US government.

The embassy said there had been threats of attacks on shopping malls, railway and metro stations and public gatherings in key urban areas, including Moscow and St. Petersburg, as well as in areas of heightened tension along the Russia-Ukraine border.

The embassy renewed its call on its nationals to leave Ukraine immediately.

In a statement, she said, the security situation in Ukraine "remains unpredictable and may deteriorate without warning."

The statement indicated that there is a strong possibility that any Russian operations will lead to the restriction of air travel.