A Russian convoy sent into Ukraine in violation of the country’s borders is the latest act of desperation from Moscow as rebels continue to lose key ground, analysts say.

In what Ukraine is calling a “direct invasion,” more than 130 trucks rolled across the border in a rebel-held part of the country Friday. Russia insists the convoy is carrying humanitarian aid, but critics called the move an attempt to arm and support pro-Russian separatists in eastern Ukraine.

The trucks started to return to Russia on Saturday.

The convoy, which had been idling near the border for nearly two weeks, moved just days before Russian President Vladimir Putin and Ukrainian President Petro Poroshenko are scheduled to attend a multilateral summit in Belarus, where top European officials will attempt to de-escalate the situation at the negotiating table.

Mark Stech, executive director of the Canadian Institute of Ukrainian Studies, says the violation of Ukraine’s borders is a strategic move by Russia to show its teeth ahead of the summit.

“Russia has had a pattern that before any major international meeting, they would … escalate their violence in order to be in a position at negotiating table (to) offer to stop that escalation and seem to have compromised something by giving up nothing,” Stech said in an interview on CTV’s News Channel on Friday.

The hostile move by Russia is a “blatant attempt” to reinforce insurgents in eastern Ukraine and de-stabilize the region, Stech said.

“They are definitely losing their fight in eastern Ukraine,” he said. “The sanctions introduced by the west are starting to work and hurt their economy, and I think they are desperate.”

Diplomatic challenge 'extremely steep'

Dominique Arel, chair of Ukrainian studies at the University of Ottawa, called the convoy’s violation of Ukraine’s borders into cities like Luhansk an “extremely dangerous development” that could lead to all-out urban warfare after weeks of intense shelling.

“How do you actually defeat an urban insurgency? It’s one thing to take one village after the other …. But urban warfare, it’s something else,” Arel said on News Channel. “I’m not sure we’re really at the end game.”

Ahead of the summit, Arel said the diplomatic challenge is “extremely steep.”

“Russia refuses to acknowledge that it is actually sending military aid to the rebels, and refuses then to acknowledge that the border between Russia and Ukraine needs to be secured,” he said.

A political settlement is ultimately necessary to bring security, Arel said.

“A claim of victory will not solve anything, especially if the border is not secure,” Arel said. “But with whom, exactly, are you negotiating? Obviously, Ukraine and Russia needs to negotiate, but at ground level, with whom are you talking to if the actual de facto …. leaders of this rebellion are actually Russian citizens… that’s the big challenge.”