Air crash investigators concluded Tuesday that Malaysia Airlines flight MH17 was shot down by a Russian-made BUK missile fired from war-torn eastern Ukraine last year killing all 298 people on board.

Even though the Dutch-led inquiry did not say who pulled the trigger, Russian officials were already disputing the findings set to further degrade strained ties between Moscow and the West.

The head of Al-Qaida's Syrian affiliate has called on jihadists in the Caucasus to attack Russian civilians and soldiers in retaliation for Moscow's air strikes in Syria.

"If the Russian army kills the people of Syria, then kill their people. And if they kill our soldiers, then kill their soldiers. An eye for an eye," Abu Mohamed al-Jolani, the head of Al-Nusra Front, said in an audio recording released late Monday.

Russian Foreign Minister Sergei Lavrov on Tuesday described the shelling of Moscow's embassy in Damascus as an "act of terror" aimed at intimidating those who support Moscow's bombing campaign in Syria. 

"It is a clear act of terror meant to scare supporters of fighting terrorism," Lavrov told reporters in Moscow, after two rockets struck the Russian embassy compound.

The Lebanese army has gone on alert along the border with Syria and inside Lebanese territories after Russian jets intensified their airstrikes in central Syria and Hizbullah got more involved in the country's war.

A security source told As Safir daily published on Tuesday that terrorist groups taking refuge in the border area are making suspicious moves.

Russia's security services said on Monday it foiled a "terrorist attack" on Moscow's public transport system by a group of militants, some of whom were trained by Islamic State jihadists in Syria.

A statement by the federal security service (FSB) said they had detained a group of people in Moscow and seized bomb-making materials they were planning to use in an attack on the capital's busy transport system.

Ukrainian President Petro Poroshenko warned Monday he had no trust in Russia's Vladimir Putin and urged the army to prepare "for the worst" despite a new truce in the separatist east.

The pro-Western Ukrainian leader's comments to servicemen in Kiev came ahead of this week's Defenders of the Fatherland Day -- an occasion of special significance in the post-Soviet republic that views the 18-month uprising in the east as Russian "aggression".

The EU demanded Monday the "immediate" halt of Russian air strikes against moderate Syrian rebel groups and warned a lasting peace was impossible under Moscow-backed President Bashar Assad.

EU foreign policy chief Federica Mogherini called Russia's military intervention in Syria an unwelcome "game-changer" that jeopardized peace efforts and risked clashes with western aircraft targeting Islamic State jihadists.

Syrian regime forces backed by Russian air strikes advanced in the center of the country on Monday, sparking the fiercest clashes with rebels since Moscow began its air campaign, a monitor said.

The Syrian Observatory for Human Rights said regime forces had entered the village of Kafr Nabuda in Hama province as they press an operation on both sides of the highway between the capital Damascus and second city Aleppo.

Russian gas giant Gazprom said on Monday it had resumed gas supplies to Ukraine, adding that Moscow had received prepayment of $234 million from Kiev ahead of the winter heating season.

"Gazprom began supplying gas to Ukraine at 10:00 am (0700 GMT) today," Gazprom chief Alexei Miller said in a statement.

Russian police have arrested a group of people they said were planning a terror attack on Moscow, the country's anti-terrorism committee said Sunday, without giving details about the group's motives.

"After a series of investigations by the security services, a group of individuals was arrested in the west of Moscow suspected of planning a terrorist attack on the capital," the committee was quoted by local media as saying.