NATO Secretary General Jens Stoltenberg on Friday called for the "full implementation" of Minsk agreements as new fighting flared up in eastern Ukraine.

"The Minsk agreements are the best possible foundation for a peaceful, political solution to the conflict in eastern Ukraine and then we have to support the full implementation of the Minsk agreements," Stoltenberg told a joint press conference with Norwegian Prime Minister Erna Solberg.

"I think it is important to understand that even though there are violations... it is important to continue to support the implementation of the ceasefire," said Stoltenberg, who was on his first official visit to Norway as NATO chief.

Stoltenberg, a former Norwegian prime minister, arrived in Norway Wednesday afternoon for a three-day visit. He met with Solberg and other senior officials earlier Friday.

Ukraine's army said Wednesday that pro-independence rebels in eastern regions had launched a "major offensive" to push deeper into the government-controlled territory, an accusation the rebels denied.

Also on Wednesday, Russian Foreign Minister Sergei Lavrov said Russia had asked the Organization for Security and Cooperation in Europe (OSCE) to establish an objective picture and report who is violating the Minsk agreements.

In an attempt to end the violence in eastern Ukraine since April 2014, a truce deal was signed on Feb. 12 in Minsk, Belarus, which covers a comprehensive ceasefire, withdrawal of all heavy weapons from the frontline and creation of a buffer zone between the two warring sides.

Ukrainian authorities said Thursday that dozens of people were killed in the east of the country over the past day, putting additional strain to the four-month-old ceasefire.