Reporters say opposition supporters were stoned
Police say there have been at least nine complaints of violent incidents since campaigning began on 26 September.
According to state television the latest incident was a battle between supporters of the ruling Alliance for Patriotic Reorientation and Construction (APRC) and the opposition alliance which left several people injured.
The trouble, which took place in Farafeni in the central part of the country, resulted in the destruction of two shops and injuries to a number of people, the report said.
Stone throwing
The election is the first since the incumbent President Yayah Jammeh last July lifted a ban on political parties. He had imposed the ban when he seized power in a military coup in 1994.
The trouble on Wednesday was allegedly started when the APRC's supporters threw stones at a convey taking the opposition candidate Ousainou Darboe to a rally in the town.
Reports say the army was called in to calm the situation and Mr Darboe, who leads the United Democratic Party which is part of the three-party alliance, was allowed to address his supporters.
Meanwhile, another opposition politician is in trouble with the law for alleged election offences.
Arrested
Omar Jallow of the People's Progressive Party of ex-president Sir Dauda Jawara is accused with seven others of assaulting a local leader of the ruling party.
But Mr Jallow, who was arrested on Monday and is the party's interim chairman whilst Sir Dauda is in exile in Britain, was released on bail to allow him time to pursue his campaign.
He is due back in court on 17 October.
A correspondent for the BBC in the Gambia says the violence is likely to continue.
The PPP is also a member of the alliance led by Mr Darboe, seen as the main challenger to Mr Jammeh.
By force
But observers believe that Mr Jammeh is heading for a victory helped by security agents who are on his side.
The Jammeh administration has been very sensitive to what it perceives as support for the opposition.
In August it asked the Deputy High Commissioner at the British High Commission in Banjul, Mr Bharat Joshi, to leave the country because it claimed his presence was considered harmful to Gambia's national interests.
The British Foreign Office said Mr Joshi had done nothing wrong.
Correspondents in Banjul said the diplomat had been asked to leave the country because he had attended the launch of the opposition alliance.