By Sergei L. Loiko and Carol J. Williams, Los Angeles Times

KIEV, Ukraine — Ukraine will never cede its strategic port of Mariupol to Russia, President Petro Poroshenko vowed Monday during a visit to the latest city in the gun sights of pro-Russia separatists.

In a defiant speech to workers at the Ilyich Mariupol metal works, the president warned that the 5-month-old conflict is far from over and ordered government troops to shore up their defenses around the city that is home to 500,000.

While major fighting has mostly subsided since the government and separatist leaders agreed to a cease-fire on Friday, a Ukrainian military spokesman in Kiev, the capital, said the pro-Russia gunmen had violated it at least five times over the weekend.

“We will do our best to achieve peace but we will be getting ready to defend our country,” Poroshenko told the hard-hat audience in remarks carried on national television. “As the commander in chief of the armed forces I have given full orders to strengthen the defenses of Mariupol.”

Poroshenko commended the military for halting the advance of Russian tanks on Mariupol that began two weeks ago. Poroshenko accused Russia of carrying out “a full-scale invasion” when two columns of Kremlin armor and troops entered southeastern Ukraine along the Sea of Azov and rolled over the town of Novoazovsk before opening an artillery barrage against Mariupol.

Shortly after the onslaught, Russian President Vladimir Putin and Poroshenko agreed on the need for a cease-fire and their representatives proclaimed one after negotiations Friday in the Belarus capital of Minsk. The 12-point plan also calls for opening peace talks and for an exchange of prisoners.

The release of captured fighters and others detained during the conflict was proceeding slowly, said Vladimir Ruban, a retired general with the nongovernmental organization mediating the exchange process.

“The government side has complicated the process with numerous bureaucratic obstacles,” said Ruban, head of the Detainees Liberation Center. “In recent days we have facilitated the exchange of only 41 of Ukraine’s soldiers and officers for nine so-called separatists.”

More than 650 Ukrainian servicemen remain in separatist custody in the Donetsk and Luhansk regions in eastern Ukraine, Ruban said.

The separatists complained Monday that they still didn’t have lists of the prisoners held by Kiev authorities.

Leonid Baranov, a security official of the self-proclaimed Donetsk People’s Republic, said on the separatist leadership’s website that their side was still holding more than 1,000 Ukrainian soldiers captive.

“Kiev says that they are holding 200-300 of our self-defense members, but there are no exact lists at this stage,” Baranov said, adding that about 1,000 separatists and local residents who support them are missing and feared to be in Ukrainian government detention.

Meanwhile, the chairman of the Organization for Security and Cooperation in Europe that helped broker the Ukraine cease-fire last week told a news conference in Geneva that he held out dim hopes of it lasting.

“We want to give it a chance,” said Didier Burkhalter. But he said he was “not optimistic at all.”

The European Union was due to expand its list of Russian officials, private citizens, and businesses to be targeted with sanctions for their alleged roles in fomenting the Ukraine crisis, which the United Nations said Monday has taken more than 3,000 lives.

In another expression of little confidence in the shaky cease-fire, European Commission President Herman van Rompuy said the new sanctions could be rolled back if the 3-day-old agreement does hold.

Before his address to the metal workers, Poroshenko vowed that the government is prepared to defend Mariupol at all costs.

“We will give away this piece of our land to no one!” he wrote on his Facebook page as he entered the front-line city.

AFP Photo

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