Gambian police have fired tear gas to disperse supporters of losing presidential candidate Ousainou Darboe as they took to the streets outside the capital Banjul to contest the re-election of President Adama Barrow.

Hundreds of protesters had gathered in the community of Serekunda, near Banjul on Monday, the day after Darboe and two other candidates said they would not accept Barrow's resounding win in Saturday's peaceful voting.

Police broke up another protest of Darboe supporters near his house in Serekunda using tear gas. A witness saw some police beating protesters, before the crowd dispersed.

The office of the Inspector General of Police said it was concerned about gatherings turning violent.

"Without restraint, any form of post-electoral violence will jeopardise our legacy for tolerance, maturity and peacefulness," a police statement said.

READ MORE:Gambia's Barrow wins presidential election

A key test for democracy

The election is a test of stability and democratic progress in the tiny West African country of 2.5 million people.

They hope it will help draw a line under the oppressive 22-year rule of former president Yahya Jammeh, who lost to Barrow in 2016 and was forced into exile.

Election observers from the African Union said the election was conducted in line with international standards, while EU observers praised the transparency of the voting and counting process.

However, in its statement, the EU observer mission criticised the Independent Electoral Commission, saying its pre-election candidate acceptance process was overly opaque.

READ MORE: Polls close in Gambia's first presidential election since Jammeh era