The central African nation of Equatorial Guinea says it thwarted an attempted "coup" in late December against the government of Teodoro Obiang Nguema Mbasogo, Africa's longest-serving leader.

The government accused at least 30 armed mercenaries from Chad, Sudan and the Central African Republic of attempting to overthrow Mbasogo with the support of Guinean opposition forces just before Christmas, a government minister said this week.

The "mercenaries ... were recruited by Equatorial Guinean militants from certain radical opposition parties with the support of certain powers", AFP news agency quoted Nicolas Obama Nchama, the country's security minister, as saying.

Nchama did not explicitly name what opposition groups or foreign powers the government believes were involved in the alleged coup.

On Wednesday, AFP reported, citing state television station TVGE, that Guinean security forces clashed with mercenaries, reportedly killing one, near the border.

The attempted putsch took place in the night between December 27 and 28, news website Jeune Afrique reported.

Military general arrested

Police in Cameroon arrested a military general from Chad among 30 heavily armed men at the Kye-Ossi border between that country and Equatorial Guinea in late December, according to Cameroon media outlet Cameroon-Info.net.

Mbasogo ordered the border be shut after the arrests, the website reported.

The opposition Convergence for Innovation party published a list of 146 activists it said were detained since the alleged coup attempt, Anadolu reported.

On December 29, however, Equatorial Guinea's ambassador to France appeared to play down the events.

"We have nothing to hide," Miguel Oyono Ndong Mifumu told Radio France International. "We cannot talk about an attempted coup. Everything is calm in Malabo."

He was later quoted by AFP as saying that an "invasion and destabilisation attempt" had been committed against the country.

Mbasogo has been in power since 1979 in the oil-rich central African nation.

"Corruption, poverty, and repression continue to plague" Equatorial Guinea under his rule, according to Human Rights Watch, and "mismanagement of public funds and credible allegations of high-level corruption persist, as do other serious abuses, including torture, arbitrary detention, and unfair trials".

In October, a French court found Mbasogo's son, Teodoro Nguema Obiang Mangue, who is also the country's vice president, guilty in absentia of embezzling tens of millions of euros from the country and laundering the money in France.

The court seized $120m worth of assets and handed down a three-year suspended prison sentence and a $35m fine.