NATO Secretary General Anders Fogh Rasmussen will visit Kiev Thursday, Ukraine's foreign ministry said, amid heightened tensions over allegations Russia is massing troops along its ex-Soviet neighbor's border.

The visit, at the invitation of Ukrainian President Petro Poroshenko, is intended to discuss an upcoming meeting on NATO-Ukraine partnership, the foreign ministry said Wednesday.

Dutch, Australian and Malaysian investigators at the eastern Ukraine crash site of downed flight MH17 are enlisting the help of local villagers in finding victims' remains and possessions, the Dutch justice ministry said on Wednesday.

"Residents are being asked to locate remains and personal belongings. They are also being given the opportunity to tell what they saw or experienced during the disaster," the ministry said in a statement issued in The Hague.

NATO Secretary General Anders Fogh Rasmussen will visit Kiev Thursday, Ukraine's foreign ministry said, amid heightened tensions over allegations Russia is massing troops along its ex-Soviet neighbor’s border.

The visit, at the invitation of Ukrainian President Petro Poroshenko, is intended to discuss an upcoming meeting on NATO-Ukraine partnership, the foreign ministry said Wednesday.

A first air strike hit the main rebel stronghold of Donetsk in east Ukraine Wednesday, as government forces preparing to retake the city said 18 soldiers were killed in clashes with rebels.

As Western countries launch each new salvo of sanctions against Russia over the Ukraine crisis, Moscow has returned fire with bans on food imports -- ostensibly for consumer protection.

Milk, cheese and onions from Ukraine, Greek peaches, Serbian prunes, Polish apples and cabbage, Spanish meat -- according to Russia's food safety regulator Rosselkhoznadzor all these products contain toxic elements, are infected with dangerous bacteria or violate other regulations.

With a scarred face and eyes red with fatigue, Ukrainian serviceman Pavel sits in a tent on the Russian side of the border, contemplating a decision he already regrets.

"We were given the order to surrender," he said wearily. "Orders are orders, but this time, I did not want to obey."

The Russian Foreign Ministry stated on Tuesday that Syria, Iraq and Lebanon are facing a “common danger” manifested in “international terrorism that does not acknowledge borders between countries and seeks to seize more lands.”

"It is necessary to denounce double standards and to abstain from taking steps that do not lead to containing the situation but on the contrary, could encourage terrorism and extremists' threats in the turbulent Middle East,” Russia's Ministry of Foreign Affairs said in a released statement.

Terrified residents on Tuesday fled the besieged rebel bastion of Donetsk in eastern Ukraine along a perilous humanitarian corridor, as government forces pushed their offensive to the outskirts of the city.

Dozens of cars packed with civilians headed along a road out of the pro-Russian stronghold, past the town of Maryinka where explosions from continuing clashes rumbled on.

Pro-Kremlin rebels in eastern Ukraine are hampering the treatment of a growing number of civilian casualties by threatening doctors, hijacking ambulances and looting medical equipment, Human Rights Watch said Tuesday.

Russia said on Monday that it will be easier to deal with the incoming new U.S. ambassador than with his "freelance" predecessor who provoked Moscow's wrath with his support for the opposition.

John Tefft, the former U.S. ambassador to Kiev, was approved as Washington's new envoy by Moscow last month. His predecessor, Stanford professor Michael McFaul, quit his post in February only two years into the job.