Gunmen have opened fire in the commercial capital of Cameroon, Douala, killing at least one person, in an apparent anti-government protest.
Reports say the gunmen were dressed in military uniforms and were carrying placards demanding that President Paul Biya step down.
Mr Biya is widely expected to win a presidential election on 9 October.
He has been in power for almost 30 years and is one of Africa's longest-serving heads of state.
In 2008 he changed the constitution to remove limits on the presidential term, provoking nationwide unrest.
'Mountain of Irregularities'
In Thursday's incident, the gunmen blockaded the mile-long Wouri bridge, shooting at police for several hours.
"A fierce exchange of gunfire ensued and one of the gunmen plunged into the River Wouri. It is not clear if he drowned," said eyewitness Itah Robert.
One witness told the Associated Press news agency that the gunmen had placards that read: "Paul Biya Must Go At All Costs" and "Paul Biya Dictator".
The security forces reportedly arrested some of the attackers.
Sporadic gunfire still could be heard in the area hours later, and armed soldiers have been deployed across Douala to search vehicles.
Twenty-two candidates are challenging 78-year-old Mr Biya in the presidential election, including John Fru Ndi, the veteran candidate of main opposition party the Social Democratic Front (SDF).
On Tuesday, the SDF denounced in the organisation of the poll.
"There is a whole mountain of irregularities," Evariste Fopoussi, the SDF's spokesman told AFP, citing double entries or missing names on electoral rolls.