LUHANSK, Ukraine — Hundreds of pro-Russia insurgents mounted a daylong assault on a border guard base in eastern Ukraine on Monday, with some firing rocket-propelled grenades from the roof of a nearby residential building and prompting the deployment of air support by government forces.
At least five rebels were killed when the guards returned fire, a border guard service spokesman said.
Some 10 kilometers (6 miles) away, a blast at an administrative building held by insurgents claimed more lives. A health official for the Luhansk region told Interfax news agency that at least seven people had been confirmed dead in the incident, which rebels described as a government airstrike.
Authorities denied carrying out a strike and said the blast was caused by misdirected rebel fire from a portable surface-to-air missile launcher.
Russia's Foreign Ministry swiftly condemned what it described as a government attack on the rebel-held building and urged U.S. Assistant Secretary of Defense Derek Chollet, who was visiting Kiev on Monday, to help calm unrest in Ukraine.
"We urge our Western partners to use their influence on Kiev, to stop Ukraine from descending into a national catastrophe," the ministry said in a statement.
On the edge of Luhansk, in the Mirny district, rebels in camouflage promised safety for troops at a border guard service base if they surrendered and laid down their arms. The pro-Russian insurgents, who have seized government and police buildings across eastern Ukraine, have waged increasingly aggressive attacks on government-held checkpoints and garrisons in an attempt to seize weapons and ammunition from Ukrainian forces.
Serhiy Astakhov, the spokesman for the border guard service, told The Associated Press by telephone that a preliminary assessment indicated that five rebels were killed and eight wounded in the attack on the walled compound on the western fringes of Luhansk, a major city not far from the Russian border. He also said seven servicemen were wounded, three seriously.
The initial attack by about 100 insurgents was met by gunfire from the border guards, and the number of attackers swelled to around 400 a few hours later. Astakhov said the Ukrainian armed forces had sent aircraft to the area, but had been unable to quell the attack. At least one fighter jet was seen flying overhead.
An AP reporter saw at least one dead rebel soldier about a kilometer (half-mile) away from the base. Fellow fighters approached and broke into tears as they viewed the body. One insurgent said the dead man was a leading rebel commander.
The fighting stopped around 1 p.m. local time but resumed a short while later with heavy gunfire heard in the area. Rebels shot at least six rocket-propelled grenades at the base compound from the rooftop of a residential building.
One insurgent fighter in uniform, who gave his name as Vlad Sevastopolsky, said pro-Russian militants have surrounded the base but offered Ukrainian troops a safe corridor out, as long as they surrender their weapons. Sevastopolsky is from a rebel group based in Antratsyt, another town in the Luhansk region.
Vladislav Seleznyov, press secretary for Ukraine's operation against the rebels in the east, described the base as an important coordinating node for the border guards, and told The Associated Press that the attack may have been an attempt to disrupt communications.
Fighting was still reportedly ongoing as darkness fell Monday.
Seleznyov also said there was another rebel attack Monday on a government checkpoint in Slovyansk, a city in the Donetsk region that has been an epicenter of the pro-Russian movement. He said rebels had set mines at a number of power plants in Slovyansk, which he claimed would be detonated if the government were to move on the city.
In the regional capital of Donetsk, gunmen from the self-proclaimed Donetsk People's Republic on Monday entered the office of the local newspaper and took away its editor, Leonid Lapa, his deputy Valery Lapshin told AP.
The gunmen told the journalists said they were taking the Vecherny Donetsk editor in for questioning. Lapshin said his editor was released several hours later.
For weeks, Russian-speaking eastern Ukraine has been the scene of deadly clashes between government troops and pro-Russian insurgents.
Many in Ukraine's east are suspicious of the new pro-Western government in Kiev, which came to power when pro-Russian President Viktor Yanukovych fled the country in February after months of street protests in Kiev. Protests in the east demanding greater freedom from the Ukrainian capital soon turned into a separatist movement, as the Luhansk and Donetsk regions declared independence following hastily called referendums.
The conflict between Ukrainian government forces and pro-Russian insurgents escalated markedly in the past week, with rebels attempting to seize a major airport and the shooting-down of a Ukrainian military helicopter.
In Moscow, the Russian Defense Ministry announced Monday a military exercise involving the launch of high-precision missiles. The ministry said the maneuvers of the western military district will continue through Thursday and will involve the deployment of Iskander surface-to-surface missiles.
Moscow didn't specify the areas where the exercise will be held and made no mention of the situation in Ukraine.
Leonard reported from Donetsk, Ukraine. Laura Mills in Kiev, Ukraine, and Vladimir Isachenkov and Nataliya Vasilyeva in Moscow contributed to this report.