Ukrainian and pro-Russian forces flexed their military muscles in the restive east of the country on Wednesday, a day ahead of high-level diplomatic talks on the escalating crisis.
Armoured vehicles from the rival sides appeared on the streets of two neighbouring towns after Russian President Vladimir Putin warned that Kiev's decision to send in troops to put down a separatist uprising in its industrial heartland had dragged the country to the brink of civil war.
NATO said it planned to deploy more forces in eastern Europe in the face of the crisis, while Germany warned of more bloodshed if the four-way talks in Geneva on Thursday fail.
An AFP reporter in the flashpoint town of Slavyansk saw at least six APCs and light tanks, some flying Russian flags, parked in the city centre with dozens of unidentified armed men in camouflage stationed around them.
Russian media said Ukrainian troops in the vehicles had switched sides to join the separatists but the Ukrainian army told AFP that it had no reports that any of its equipment had been seized.
An AFP reporter in the nearby town of Kramatorsk also said Ukrainian forces had deployed a column of 14 armoured vehicles, although these were being blocked by a crowd of pro-Russian protesters.
Military jets could be seen flying low over both towns in an additional show of strength.
As the situation on the ground appeared to escalate, the authorities in Kiev ratcheted up the verbal attack on Russia, with Prime Minister Arseniy Yatsenyuk accusing Moscow of trying to build "a new Berlin wall".
Yatsenyuk demanded Moscow halt its alleged support for the separatists but said Kiev remained committed to Thursday's crunch talks between the top diplomats of Russia, the European Union, the United States and Ukraine.
"There is only one directive for the Ukrainian foreign ministry — the Russian government has to immediately withdraw its commando groups, condemn the terrorists and demand they leave the installations," he said.
Ukraine's acting Defence Minister Mykhailo Koval on Wednesday headed out to the east to check on the progress of Kiev's seemingly stalled bid to oust the separatists.
Ukraine's military also pledged a firm response after two serviceman were allegedly taken hostage by pro-Russian forces in the Lugansk region.
The Ukrainian Security Service (SBU) said in a statement that Russian commanders in the east had issued pro-Kremlin militants with "shoot-to-kill" orders.
Elsewhere, pro-Moscow gunmen stormed the mayor's office in the regional capital of Donetsk, according to an AFP reporter at the scene.
