PODGORICA, Montenegro (AP) — It all started with a video posted on social media: a secret recording from 2016 that appears to show a well-known local tycoon hand over an envelope containing bundles of cash to a party associate of Montenegro's long-standing leader.

The prominent businessman, a former close friend and confidant of Montenegrin President Milo Djukanovic, released the video late last year in retaliation for charges filed against him for fraud and money laundering.

The so-called envelope affair has triggered weeks of anti-Djukanovic protests, demanding the resignation of one of Europe's longest-lasting leaders after his almost 30 years in power.

The almost simultaneous eruption of strong anti-government movements in neighboring Serbia and Albania has prompted talk of a "Balkan Spring" in reference to a wave of protests across the Arab world in 2010.