Russia's recent military build-up in Syria aims not only to boost the embattled regime of crucial ally Bashar Assad but also to send a strong signal to the West, experts say.

With President Vladimir Putin set to make Syria a key issue of his address to the U.N. General Assembly in New York later this month, Moscow is making it clear that it will not be ignored in the Middle East.

Ukraine redoubled its efforts Wednesday to see Russia stripped of its veto power on the U.N. Security Council when the global body's General Assembly meets in the coming weeks.

Numerous nations are upset with Russia for being one of the five permanent council members that together with China has blocked a series of U.N. efforts to impose sanctions on Syrian President Bashar Assad's regime.

The Kremlin denied a claim by a senior negotiator Wednesday that Russia had offered in 2012 to make Syrian President Bashar Assad step down in an "elegant way", saying it never called for regime change.

"I can only once more repeat that Russia is not involved in changing regimes. Suggesting that someone step aside -- elegantly or not -- is something Russia has never done," President Vladimir Putin's spokesman Dmitry Peskov told journalists, quoted by TASS state news agency.

Prime Minister Benjamin Netanyahu will travel to Russia next week for talks with President Vladimir Putin on Moscow's military support for the Damascus regime and "threats" facing Israel, his office said Wednesday.

Netanyahu will speak about "the deployment of Russian military forces in Syria," a statement said.

Washington warned Russia on Tuesday that Syrian leader Bashar Assad has no role in coalition operations against the Islamic State group and must step down to allow a political settlement.

Secretary of State John Kerry called his Kremlin counterpart Sergei Lavrov to restate the U.S. position after Russia's President Vladimir Putin promised to maintain military support for Assad.

Russia on Tuesday began hearing a case against two Ukrainians accused of murdering dozens of Russians during the Chechen war in the 1990s as part of a nationalist killing squad.

The powerful Investigative Committee said that the supreme court of Chechnya -- the highest court in the region -- has begun to hear the case against Stanislav Klykh and Mykola Karpyuk, both of whom have been in pre-trial detention for over a year on charges of murder and belonging to a militant organization.

Russia has sent artillery units and seven tanks to a Syrian air base as part of Moscow's continued military buildup in the war-ravaged nation, a U.S. official said Monday.

The increase of Russian hardware in Syria has caused concerns in the West about the implications of Moscow militarily helping its old ally, President Bashar Assad.

EU member states formally approved on Monday a six-month extension of sanctions against Ukrainian and Russian figures accused of backing pro-Moscow rebels fighting to break away from Kiev.

"The assessment of the situation did not justify a change in the regime of sanctions nor in the list of persons and entities under restrictive measures," the EU's Council of Ministers said in a statement.

NATO member Poland on Monday signed a deal on military cooperation with non-member Sweden amid concerns raised by increased Russian military activity in the Baltic. 

"Once a sea of peace, the Baltic has become a sea of danger," Polish Defense Minister Tomasz Siemoniak told reporters at a joint press conference in Warsaw with Swedish counterpart Peter Hultqvist.

Russia on Monday launched its largest military exercises of the year, Center-2015, involving some 95,000 soldiers including ground troops, navy and airforce units.

The long-announced war games are "the most large-scale drill of 2015," the defense ministry said.