The recruiting office in Moscow for the Donetsk People's Republic doesn't have a street address, but volunteers can join by calling a number or writing an e-mail.
Even the U.S. State Department acknowledged last month that the office exists and that Russia allowed it.
Word of the recruiting effort is spread through colorful fliers and banners calling on Russians to "Join Strelkov's Army" — referring to Igor Strelkov, a former Russian security officer who heads the insurgency's militia — that are displayed at rallies in Moscow and are ubiquitous on the Internet.
The recruiting comes as the Ukrainian military is intensifying its campaign against the pro-Russian insurgents and is closing in on the largest rebel stronghold of Donetsk in eastern Ukraine.
At the same time, Russia has amassed about 20,000 combat-ready troops on Ukraine's eastern border, according to NATO.
Detailed instructions about the recruitment office appeared in June on Russia's VKontakte social network, on the page of the Donbass People's Militia.
Some Russian websites reported having recruitment posts as early as May.
The VKontakte page included a phone number and e-mail address for the militia, but phone calls went unanswered.
Artur Gasparyan, a volunteer fighter from Armenia, told Russia's Radio Svoboda that after his second attempt to contact the VKontake group, several unidentified men scheduled a meeting with him and 10 other recruits in Moscow before he was sent to fight in eastern Ukraine.
Ukraine and the West accuse Russia of arming the insurgents who seized government buildings in the cities of Donetsk in April, proclaimed independence from Kiev and pledged closer ties to Russia.
Kiev then launched its offensive against the insurgents.
According to the United Nations, about 1,500 people, including hundreds of civilians, have been killed in the clashes.
The U.S. and others say that weapons are continuing to cross from Russia into Ukraine — possibly including surface-to-air missiles that downed a Malaysia Airlines jetliner last month, killing all 298 on board.
Russia maintains it is not arming the rebels.
Support for the insurgency is widespread in Russia, where a majority of the population views the rebels as fighting a pro-Western regime they think is hostile to Russian-speaking people who live in Ukraine.
"If weapons and aid are going into eastern Ukraine, then that cannot be happening without the approval of the Kremlin," said Alexander Konovalov, president of the Moscow-based Institute of Strategic Assessments.
"Several different (factions) of the Kremlin might have their own policies, but one man approves this," he said, referring to Russian President Vladimir Putin.
Amid that support, public efforts to gather aid are widespread — whether for volunteers, supplies or money.
A flier from Strelkov's militia requesting "humanitarian aid" listed a variety of combat gear, such as army boots, optical sights for AK-47s, night-vision glasses and camouflage.
The equipment is being gathered by a group called the Foundation for Aid to Novorossiya and Donbass.
During a Moscow rally last week, the group filled a 5-ton truck with food, clothes and military equipment.
Among the donated items was a generator for an armored personnel carrier, the foundation said.
"Ordinary people will get this aid. Of course, some of this is for the militiamen. It will go straight to the leadership of the Donetsk People's Republic," said Sergei Zakharov, a resident of Kramatorsk, Ukraine, who was in Moscow to help the foundation, as men loaded boxes into the truck.
The group said it raised 6.2 million rubles (about $177,500) in just over a month between June and July.
Source: USA Today