Mustapha Adib, a little-known diplomat who was nominated to become Lebanon's new prime minister Monday, faces the nearly impossible challenge of embodying change after being picked by the political establishment.

Adib has been Lebanon's ambassador to Germany since 2013 and his name only emerged on Sunday to replace Hassan Diab, whose government resigned in the aftermath of the deadly August 4 blast at Beirut port.

The 48-year-old was born in the northern city of Tripoli and is a Sunni Muslim, making him eligible to become prime minister under Lebanon's sectarian-based power-sharing system.

His biography on the Berlin embassy website presents him as an academic who holds a PhD in political science.

It says he has conducted "research and expert work in the areas of both human and state security, parliamentary oversight of the security sector, decentralisation and local democracy, and electoral laws".

From 2000 to 2004, he served as an advisor to Najib Mikati, a billionaire and former prime minister who backed his nomination on Monday.

In 2011, then-prime minister Mikati appointed Adib as his chief of cabinet.

Former premiers Saad Hariri and Fouad Siniora also threw their weight behind Adib after two other candidates were reportedly rejected by the dominant Shiite Muslim group Hezbollah and its political allies.

His appointment came on the day French President Emmanuel Macron was due to arrive for another landmark visit.

An acquaintance of Adib from Tripoli who asked not to be named described him as "calm, courteous and diplomatic".

"He is not a man of confrontation and does not take strong stances, but avoids problems and strives to solve them diplomatically with a view to consolidating his relationship with different sides," the acquaintance said.

Opposition groups representing the protest movement that erupted last year to demand the wholesale removal of a political class seen as corrupt and incompetent rejected Adib's nomination before it was even confirmed.

Activists on social media were quick to compare Adib to Diab, who had promised to lead Lebanon's first government of technocrats when he took office in January but showed no ability to break from his political sponsors.

Lebanon Rises Up -- Germany, a Facebook page representing Lebanese activists in Germany, told AFP that Adib was a product of the past and could not embody change.

"We see no change for the better in Ambassador Mustapha Adib being named, as he is subject to the quota system in place in Lebanon," the group said in a statement.

It claimed that Adib himself, who was not a career diplomat when he was appointed to Berlin seven years ago by a Mikati government, owed his job to the former prime minister and to Lebanon's sectarian quotas.