(Adds fighting in Slaviansk church, details from border)
By Thomas Grove
MARYNIVKA, Ukraine, June 6 (Reuters) - Pro-Russian separatists operating from the grounds of a church in the eastern city of Slaviansk killed a member of the Ukrainian interior ministry's special forces and seriously wounded two others in a mortar attack on Friday, the ministry said.
Slaviansk has been at the heart of a two-month insurgency in the Russian-speaking east by rebels opposed to the overthrow of a Moscow-leaning president and the formation in Kiev of a pro-European government.
"One employee of the Ivano-Frankivsk special police unit and two employees were heavily injured in the attack," the ministry said in a statement on its website.
Fighting in the eastern regions of Donetsk and Luhansk has intensified since the landslide election of Petro Poroshenko as president on May 25 which followed the fall and flight of the pro-Moscow Viktor Yanukovich in February.
The new incident took place on the eve of the inauguration in Kiev of Petro Poroshenko as president. The pro-Western businessman has promised to unveil a peace plan soon to end the rebellions in the east.
Poroshenko was in France on Friday for the commemoration of the Allied D-Day landings in World War Two, where he met world leaders including Russia's Vladimir Putin who denies charges by Kiev and the West that Moscow is actively supporting the separatists.
Late on Thursday, Ukrainian forces fended off an attack by separatists on a border post about 95 km (60 miles) to the east of Donetsk.
The Border Guard service said five Ukrainian personnel were wounded in Thursday's attack and, according to its "preliminary information", 15 separatists had been killed in the attack.
"They drove around us in circles shooting for about four or five hours," said Vadim, an officer at the border post wearing a camouflage T-shirt and cap with the Ukrainian trident on it.
"They didn't ask us to give up, lay down our weapons, or make any attempt to communicate at all. They just shot," he said, adding he hoped reinforcements would arrive "soon". He said there were 100-150 attackers.
The rebels' two armoured personnel carriers, one of which had the name of the separatist formation "Battalion Vostok" painted on it, and a military transport vehicle covered in bulletholes stood abandoned at the checkpoint.
A spokesman for the Vostok Battalion was unavailable for comment. A spokeswoman for the separatists said she had no information about losses from the rebel side.
Kiev accuses Moscow of fomenting the rebellion, sending arms, mercenaries and funds across the long porous border. The Ukrainian government has promised to send reinforcements to help border guards who are increasingly being ambushed. (Additional reporting by Richard Balmforth; Writing by Sabina Zawadzki; Editing by Andrew Roche)