Rasmussen served as Danish Prime Minister and NATO chief | Paul Morigi/WireImage Former NATO chief becomes adviser to Ukraine’s Petro Poroshenko Anders Fogh Rasmussen: Situation in Eastern Ukraine is ‘alarming,’ but Kiev must implement reforms.

Anders Fogh Rasmussen, former NATO Secretary General and Danish Prime Minister said on Saturday he's accepted the appointment of Ukraine’s President Petro Poroshenko to become his adviser.

Rasmussen, who had held NATO's top post from 2009 to 2014, wrote on his Facebook page that he is “pleased to accept the appointment." He said he will do everything “to promote security and reforms in Ukraine and strengthen the Ukraine-EU bond.”

The security situation in Eastern Ukraine, where Ukrainian forces have been fighting Russia-backed rebels since 2014, "is alarming," Rasmussen said, calling for the Minsk agreement to be "fully implemented by all sides."

Also, Ukraine must implement "much needed reforms, including an enhanced fight against corruption," Rasmussen said and emphasized that "reinforced ties with the EU are essential" for the process to move forward.

"I look very much forward to working with the Ukrainian authorities,” Rasmussen said.

Pleased to accept pre. @poroshenko's appointment as advisor. Will do my utmost to promote security, economic reforms and stronger EU ties — AndersFogh Rasmussen (@AndersFoghR) May 28, 2016

The appointment angered Russian MPs, with the deputy head of the foreign affairs committee telling Interfax press agency that "it's a hostile gesture [by Ukraine]."