Angola's President Jose Eduardo Dos Santos quietly marked 30 years in power on Monday, with no public celebrations about the milestone reached by Africa's second longest serving leader.

State-owned daily Jornal de Angola, which most days carries a picture of the 67-year-old leader on its front page, made no reference to the anniversary and no official events appeared on the public diary.

Only at the end of the day did state news agency ANGOP run a story in which Dos Santos was praised for his "undeniable intelligence, his high sense of tolerance and brotherhood and his great vision and foresight".

"The MPLA does not have the slightest doubt that the life of President Jose Eduardo dos Santos, from his teenage years until today, has been marked by his absolute dedication to Angola and the Angolan people," it quoted the ruling party as saying.

Dos Santos's three decades at the helm of the oil-rich nation come four days after an annual public holiday celebrating his predecessor, Angola's first president Agostinho Neto, which included parties and educational seminars.

"Today's lack of celebration is deliberate so as not to draw attention to how long Dos Santos has been in power," independent journalist and Angolan commentator Rafael Marques told AFP.

"If there was a big celebration, it would be an opportunity for the independent media to criticise the president."

Opposition parties and rights groups claim Dos Santos is clinging to power by deliberately delaying presidential elections.

A presidential poll - the first since 1992 and only the second to take place since independence from Portugal 34 years ago - had been put off this year until a new constitution outlining the electoral system is adopted.

The MPLA (Popular Movement for the Liberation of Angola) won 81 percent of the vote in the 2008 parliamentary election, the first to be held in Angola in 16 years.

The election came as Angola was enjoying an economic boom thanks to high oil prices but the country, which relies on oil for 90 percent of its income, has seen its reserves plunge due to lower oil prices and public spending has been cut as a result.

Dos Santos is now Africa's second-longest serving lead after Moamer Kadhafi of Libya, following the death in June of Gabonese leader Omar Bongo, who led his country for 41 years.