Mauritanian President Mohamed Ould Abdel Aziz arrived in Gambia on Wednesday to talk to President Yahya Jammeh, Gambian state TV said, in what might be the latest mediation effort to persuade Jammeh to step down to defuse a political crisis.

Jammeh is refusing to step down despite losing an election to challenger Adama Barrow.

State TV did not give any specific reason for the visit.

Timeline of The Gambia's electoral crisis

Here is a timeline of developments since the December election in which President Yahya Jammeh of the Gambia lost to opponent Adama Barrow:

- Jammeh concedes defeat -

- December 1, 2016: Gambians go to the polls to choose their new president from three candidates, including incumbent Jammeh, who has ruled with an iron fist for 22 years, and Barrow, representing a large opposition coalition.

A day later the electoral commission announces that Barrow has won, to scenes of jubilation on the streets.

Jammeh concedes defeat, congratulating Barrow for his "clear victory", adding: "I wish him all the best and I wish all Gambians the best."

- December 3: Barrow holds talks with his team to plot his transition to power, telling reporters: "We are not witch-hunting anybody, nothing is personal."

- Opposition freed -

- December 5: Gambian opposition leader Ousainou Darboe, who was jailed in July for taking part in a protest, is freed on bail with 18 others.

In the following days, some 40 other members of the opposition are also freed.

- Jammeh U-turn -

- December 6: The electoral commission says that Barrow has won the election more narrowly than originally thought, and with a lower turnout. He garnered 43.2 percent and Jammeh 39.6 percent of the vote. Third party candidate Mama Kandeh took 17.1 percent.

- On December 9 Jammeh announces he has changed his mind, saying: "In the same way that I accepted the results faithfully believing that the Independent Electoral Commission was independent and honest and reliable, I hereby reject the results in totality."

He lodges a complaint with the Supreme Court to overturn the result.

The defiance sparks global concern, with the UN Security Council among those demanding Jammeh hand over power.

- Jammeh urged to go -

- December 13: Heads of state from West African regional bloc ECOWAS are sent to Gambia, but do not manage to persuade Jammeh to acknowledge his defeat. A new mission takes place a month later.

- On December 31 Jammeh accuses ECOWAS of declaring "war".

- Supreme Court stalls -

- January 4, 2017: The army chief reaffirms his loyalty to Jammeh.

- January 9: Jammeh fires 12 ambassadors after they called for him to step aside. Several ministers have since been fired or resigned.

- January 10: The Gambia's chief Supreme Court justice says Jammeh's legal challenge against the result will not be heard for several months.

- January 13: The African Union (AU) urges Jammeh to respect the results and quit power peacefully, warning of "serious consequences". It says it will not recognise him "as of 19 January 2017".

Thousands of Gambians fearing unrest cross the border into neighbouring Senegal and further afield to Guinea-Bissau, according to the United Nations refugee agency and Guinea-Bissau officials.

- Barrow in Senegal -

- January 15: Senegalese President Macky Sall announces that he has agreed to "welcome Gambian president-elect Adama Barrow in Dakar until his inauguration," on January 19.

- January 16: The Gambia's top judge pulls out of hearing a bid by Jammeh to halt the inauguration. Seven foreign journalists are barred from entering the country.

- State of emergency -

- January 17: Jammeh declares a state of emergency, saying foreign powers had created an "unwarranted hostile atmosphere, threatening the sovereignty, peace, security and stability of the country," forcing him to act.