MOSCOW - Conflicts in Syria have intensified over the week despite the Russia-US truce accord which started on Monday, as militants continued targeting Syrian government troops, the Russian Defense Ministry said Sunday.

"Only the Syrian government forces have observed the cessation of hostilities over the past six days since it came into effect... while militants attacks against the Syrian army are on the rise," the ministry's spokesman Maj. Gen. Igor Konashenkov said.

The Untied States failed to help separate terrorists from the so-called moderate opposition, and neither did it exert necessary pressure on them, Konashenkov added.

The situation is especially grave in the northern city of Aleppo, where movements of armored vehicles and cars have been recorded in the eastern part of the besieged city and its suburbs, said the spokesman.

On Sept 10, Russian Foreign Minister Sergey Lavrov and US Secretary of State John Kerry announced a nationwide cease-fire in Syria, which demands all warring sides stop attacks and airstrikes, and allow access to besieged areas, including Aleppo.

The cease-fire deal is now threatened with a recent escalation between Moscow and Washington, after the U.S.-led coaliton airstrikes killed 90 Syrian servicemen in the eastern province of Deir al-Zour on Saturday.

The Russian Foreign Ministry said earlier on Sunday that the move would "put the implementation of the agreement in danger."