NATO has expressed fears of a Russian military push beyond Crimea into eastern Ukraine and further south to Moldova’s breakaway Transdniestria.

U.S. Air Force General Philip Breedlove, NATO's Supreme Allied Commander in Europe said the Russian force massed at the Ukrainian border «is very, very sizable and very, very ready.»

The top NATO commander told an event held by the German Marshall Fund think tank that he was very concerned about the threat to Transdniestria.

There is absolutely sufficient [Russian] force postured on the eastern border of Ukraine to run to Transdniestria if the decision was made to do that and that is very worrisome.»

Russia is acting much more like an adversary than a partner,» the U.S. general said.

Transdniestria, a Russian-speaking industrialised region of Moldova, broke away from the former Soviet state in 1990. In 2006 Transdniestria overwhelmingly voted in a referendum to join Russia, but Moscow ignored the vote as it tried to work out a confederation arrangement for Moldova. After Crimea’s referendum on splitting from Ukraine and reuniting with Russia, the Speaker of Transdniestria’s Parliament appealed to his Russian counterpart in the State Duma lower house to provide legislative possibilities for the region’s accession to Russia.

However, Speaker of the Russian Parliament’s upper house said the absorption of Transdniestria or Georgia’s breakaway regions of Abkhazia and South Ossetia were not on the agenda «at this stage.»

The three self-proclaimed republics «have not asked for joining Russia; it is inadvisable at this stage to talk about this,» Speaker Valentina Matviyenko said in an interview. «One should not portray Russia as a country bent on seizing territories. This question is not on the agenda.»

Russia’s top defence official has also sought to dispel Western fears of a Russian military move into Ukraine.

Russia is complying with all international agreements on troop limits near its border with Ukraine,» said Deputy Defence Minister Anatoly Antonov.

Mr Antonov told reporters on on Saturday that eight eight groups of foreign monitors from nine Western nations carried out inspections of Russian troop deployments near Ukrainian borders.

The inspectors «have not established any undeclared military activity that could pose a threat to [Russia’s] neighbouring countries,» he said.

In Crimea, the Russian flag is now flying over 189 Ukrainian military installations, the Russian defence ministry said on Sunday, a day after pro-Russian forces stormed and seized the Belbek air force base, Ukraine’s last major military facility in the peninsula. The Ukrainian commander of the airbase was detained after the takeover, but released on Sunday.

In the eastern Ukrainian city of Donetsk pro-Russian demonstrators again rallied on Sunday in support of their demand for a referendum on greater autonomy from Kiev.

Russia’s closest ally Belarus President Alexander Lukashenka voiced concerns that Crimea had set a «bad precedent,» even as he admitted that the region was now «de facto» a part of Russia.

The statement reflected the unease Belarus and other post-Soviet states feel over Russia’s annexation of Crimea.

At the same time the Belarus leader blamed Ukraine’s new government for provoking Russia.

Why did they ban the Russian language after coming to power and put pressure on Russian-speakers?» he told journalists on Sunday. «They gave a pretext and reason for Russia to intervene.»