* Diplomat declared persona non grata
* Accused of collecting intelligence on NATO cooperation
* Ukraine says Russia behind uprising in east
* Ukraine "helpless" to restore order (Updates with accusations, detainee release)
By Natalia Zinets and Matt Robinson
KIEV, May 1 (Reuters) - Ukraine ordered the expulsion of Russia's military attaché, saying it had caught him "red-handed" receiving classified information on the country's cooperation with NATO during an armed uprising Kiev says is directed from Moscow.
The Foreign Ministry said on Thursday the diplomat had been detained a day earlier and declared persona non grata.
Ukraine's security service said he was a Russian intelligence officer who had been collecting intelligence on "Ukrainian-NATO military and political cooperation".
"On April 30, he was caught red-handed receiving classified material from his source," said Maryna Ostapenko, a spokeswoman for Ukraine's security service, the SBU. She described the source as a colonel in the Ukrainian armed forces.
Ukraine says Russia stands behind the fall of towns and cities over the past month in the country's industrial east to pro-Russian separatists, often involving well-organised masked gunmen in military fatigues.
Russia denies having any part in the rebellion, but has warned it reserves the right to intervene to protect ethnic Russians - following its annexation of Crimea in late March - and has massed tens of thousands of troops on its western frontier with Ukraine.
Ostapenko said the attaché had been handed over to the Russian embassy and ordered to leave, though she was not sure if he had yet done so.
There was no immediate response from Moscow, which like Kiev was observing the May 1 holiday.
Ukraine's pro-Western leaders conceded on Wednesday they were "helpless" to counter the fall of government buildings and police stations to the separatists in the Donbass coal and steel belt, source of around a third of the country's industrial output.
Having seized key buildings in the capital of the easternmost province, Luhansk, on Tuesday, gunmen took control at dawn on Wednesday in the nearby towns of Horlivka and Alchevsk. Thursday was relatively quiet.
Following a now familiar pattern, local media reported that some 30 armed men had seized the town hall in the small town of Amvrosiivka near the border, home to around 19,000 people, and forced the mayor to sign his resignation. They hoisted the Russian tricolour.
In Donetsk, the biggest city to fall with around 1 million people, mainly Russian-speaking separatists have declared a "People's Republic of Donetsk" and called a referendum on secession for May 11, threatening to undercut a planned presidential election in Ukraine two weeks later.
Ukraine hopes the presidential poll will help restore order after five months of civil turmoil that saw Moscow-backed president Viktor Yanukovich toppled after street protests and gun battles in central Kiev, and Russia's subsequent annexation of the Crimean peninsula.
Pro-Western authorities that took power with Yanukovich's overthrow accuse Russia of planning to disrupt the presidential election, create instability and frustrate the new government's hopes of Western integration.
Overnight, the state security guard, responsible for securing key government sites and officials, carried out a small drill in central Kiev. Four armoured personnel carriers trundled through the streets to parliament, where several dozen troops took position as if responding to a threat.
The guard's commander, Valery Galetey, said they were training for possible "provocations" during the May 25 election. (Additional reporting by Sergei Karazy; Writing by Matt Robinson; Editing by Giles Elgood)
Our Standards: The Thomson Reuters Trust Principles.