LUHANSK, Ukraine -- Pro-Russian insurgents overran and seized two government bases in eastern Ukraine, overpowering National Guard forces who ran out of firepower and hauling off ammunition and explosives from a border post.

The twin setbacks highlighted the ineffectiveness of Ukraine's poorly trained and cash-starved armed forces, which have struggled to uproot the mutiny that has engulfed the nation's industrial heartland.

Ukraine's fledgling government has blamed the recent military failures on pro-Russia former President Viktor Yanukovych, claiming that his corrupt government starved soldiers of resources and training.

President Barack Obama, who met Wednesday with Ukraine's president-elect in Warsaw, offered $5 million in new aid to the nation's beleaguered military that could help in the fight against the insurgents.

In 10 hours of fighting overnight at the National Guard base near the eastern city of Luhansk, six militants were killed and three Ukrainian servicemen were injured, officials said in a statement Wednesday. Rebel fighters took control after the guardsmen ran out of ammunition, the National Guard said.

Rebels also seized a border guard base on the outskirts of Luhansk following a nearly two-day-long siege. An Associated Press reporter saw pro-Russian militia carrying crates of ammunition and explosives out of the base Wednesday and driving away in border guards' cars.

Alexei Toporov, a spokesman for the insurgents in Luhansk, said the guards were fleeing, and the insurgents did not try to detain them.

"We released them and let them go home, we impeded nobody," he said. "They left their weapons, and this base is now coming under the control of the Luhansk People's Republic."

Ukraine's Border Guards Service said on Wednesday that the troops from that outpost had been evacuated to unspecified "safe locations."

There was no immediate report of casualties in the fighting at the border guard base. Border guards answer directly to Ukraine's president while the National Guard is part of the country's police.

The Defence Ministry set up a charity account to support the armed forces while volunteers across the country have been buying provisions for the soldiers.

The fighting in Ukraine's east has escalated following the May 25 presidential election won by billionaire candy magnate Petro Poroshenko, with rebels launching an attack on a major airport, shooting down a government helicopter and besieging a number of military bases.

Trying to regain the initiative, Ukrainian troops on Tuesday launched an offensive against pro-Russian insurgents in Slovyansk, a city that sits on a strategic highway about 90 kilometres (55 miles) north of Donetsk, the largest city in the east.

Two government soldiers were killed and 42 injured in daylong fighting, Vladislav Seleznyov, press secretary for Ukraine's operation against the rebels in the east, told Ukrainian news agencies. Seleznyov put the death toll of the rebels at 300 but the insurgents rejected these reports.

After a day of fierce fighting, government forces managed to dislodge rebels from the town of Krasny Liman, just east of Slovyansk.

Obama on Wednesday praised Poroshenko for reaching out to Ukraine's restive east. The White House also said the $5 million in aid would include, for the first time, body armour and night-vision goggles for the use of troops. The United States already has provided ready-to-eat meals and money for medical supplies and other non-lethal assistance, including clothing, sleeping bags and generators.

In Kyiv, Interim President Oleksandr Turchynov -- who will hand over to Poroshenko on Saturday -- asked Ukraine's Security and Defence Council late Tuesday to consider imposing martial law in parts of eastern Ukraine in a bid to stabilize the situation.

Deputy prime minister Vitaly Yarema was quoted by the Interfax news agency as saying that the council will convene to discuss martial law only after Poroshenko's inauguration.