Bulgaria's six-month EU presidency stint Thursday got off to a noisy start as anti-corruption protesters blocked streets in heavily-guarded capital Sofia.

More than 1,500 people shouted "Mafia!", "Resign!", "Save Pirin" and "We want nature, not concrete" to slam plans for the country's Pirin national park they say would open to construction almost half of the UNESCO world heritage site.

Many demonstrators carried banners denouncing corruption in the poorest EU member state 10 years after it joined the bloc.

"Corrupt we stand strong" one banner read, mocking the "We stand strong" motto of Bulgaria's EU Presidency which runs to July.

Several hundred demonstrators from the southwestern regions of Bansko, Dobrinishte and Blagoevgrad meanwhile staged another rally, backing plans for more extensive winter tourism development in Pirin and the construction of a second chair lift to ease chronic queues of skiers at the popular Bansko resort.

Both rallies passed off peacefully but rush hour traffic came to a standstill in Sofia with much of the city centre sealed off ahead of a concert to mark the Presidency opening.

A heavy police presence was on hand for the arrival of EU Commission President Jean Claude-Juncker, European Parliament chief Antonio Tajani, EU Council President Donald Tusk and all EU Commissioners.

Police also cordoned off the area around Bulgaria's parliament as several smaller rallies took place.

Pensioners demanded a rise in their minimum retirement pay, a small anti-NATO and anti-EU crowd gathered to burn the EU flag and shout "NATO out" and about a hundred people demonstrated against domestic violence.

Some police also demonstrated for higher pay, winning a pledge for an additional 50 million euros from Prime Minister Boyko Borisov.

Policemen themselves staged several small rallies during the day to demand higher pay and managed to receive a pledge for an additional 50 million euros by Prime Minister Boyko Borisov.

Bulgaria's EU Presidency Minister Lilyana Pavlova slammed the protests, saying they were out to attract attention on the day when Bulgaria's capital Sofia was a focus of international attention.

Borisov meanwhile stated Sofia is looking to enter the "waiting room" to join the euro with European Commission chief Jean-Claude Juncker having called for the eurozone to expand beyond its current 19 members.

"Your place is in the euro and we shall work on it," Juncker said in a speech.

"Bulgaria has a stable currency, growth of four percent, low unemployment. We are ready to join the waiting room for the euro," said Borisov, adding Bulgaria had told European Central Bank chief Mario Draghi that "we have done our duty."

Finance Minister Vladislav Goranov said the country wanted to launch the procedure with the ECB "in the first quarter" of the year.