Ukraine's acting foreign minister, Andriy Deshchyta, said he won't respond to "Kremlin-orchestrated provocations" in the east of the country in which several people have been killed.

Two people were died and several wounded in a shootout in the eastern Ukrainian city of Kharkiv late on Friday night, according to Ukraine's acting interior minister, Arsen Avakov.

"We have studied the experience of Georgia. We need to be more creative," Deshchyta told a press conference in Kiev on Saturday.

Asked if he expected Russia to invade eastern Ukraine next week, once the referendum in Crimea was over, he said: "Perhaps you should ask this to Putin. We are ready to stand up to aggression. We are in constant talks with our partners. Our position is to solve this crisis using peaceful means."

In the 2008 Russian-Georgian war, Georgia's then president responded to cross-border shelling from the rebel province of South Ossetia by ordering a major military attack on the enclave, which in turn triggered a full-blown Russian invasion.

Deshchyta said: "Since there is a kind of diplomatic war between Ukraine and Russia we can't reveal all our plans."

He said the new government in Kiev was prepared to discuss greater autonomy for Crimea, but only with the proper legal authorities there, and not while there were "guns on the streets". He described Sunday's referendum as "totally illegal".

Avakov wrote on his official Facebook page early on Saturday that around 30 people "from both sides" had been arrested during a shootout late on Friday.

The Russian state news agency Itar-Tass reported that shots had been fired from the offices of the far-right Ukrainian nationalist group Right Sector.

But the Ukrainian authorities accused Russia of provoking the gunfight.

Kharkiv's governor accused Russian activists of fomenting violence and urged people not to be goaded into fighting back.

"Tonight's incident was a well planned provocation by pro-Russian activists," said Ihor Baluta.

He said people on a minibus had deliberately provoked a dispute with a group holding a pro-Russia demonstration before driving off again.

Pro-Russian activists came in pursuit and found the van parked by a building containing offices of Ukrainian nationalist groups, and fighting began.

"Hired provocateurs from a neighbouring country are staging professional provocations," Avakov said. He accused allies of the ousted president Viktor Yanukovich of financing unrest in eastern Ukraine, aided by "extremist Russian forces".

Violence has escalated in Ukraine's east in recent days, as pro-Russia demonstrators have seized government buildings and clashed with supporters of the new Kiev government. At least one person died and 17 were wounded in clashes in the city of Donetsk on Thursday.

The violence overnight follows the failure on Friday of 11th-hour talks in London between the US secretary of state, John Kerry, and his Russian counterpart, Sergei Lavrov.