Cameroon's ruling party has won a landslide victory in last Sunday's elections, according to provisional results released late Monday.
President Paul Biya is rumoured to want another term in office
But opposition parties allege "massive fraud" in the parliamentary and municipal polls.
The opposition also say they will challenge the results in court.
President Paul Biya's Democratic Rally of the Cameroonian People (RDPC) won at least 152 of the 180 seats in the National Assembly.
The RDPC had 149 seats in the outgoing parliament, Cameroon's minister for territorial administration, Marafa Yaya, told reporters.
Turnout among some five million registered voters was 62%, Mr Yaya said.
The opposition says the RDPC might try to use its two-thirds majority in the assembly to amend the constitution to allow Mr Biya, already head of state for 25 years, to seek a new term in 2011.
The main opposition Social Democratic Front (SDF) is down from 22 to 14 deputies in the chamber while the Cameroonian Democratic Union (CDU) lost one of the five seats it held before.
Smaller parties won a further three seats and seven remain to be decided.
In the municipal polls, the governing RDPC won 303 out of 363 communes.
"Fraud attempts and fraud have been reported - at least one case of ballot box stuffing and the majority of people are voting without identity Cards," Jacob Beide, head of an observer group told reporters at the end of voting on Sunday.
Like its western neighbour Nigeria, oil-rich Cameroon is regularly listed among Africa's most corrupt countries by Transparency International.
Critics also accuse Mr Biya of trampling on democracy and human rights.