About 50 protesters gathered outside Gambia's embassy in Senegal on Thursday to demand that President Yahya Jammeh halt the mass execution of prisoners and press the international community to intervene.

The protesters chanted "Yahya assassin! Jammeh criminal!" and "Jammeh to the ICC (International Criminal Court)" as they crowded in front of the embassy of the smallest nation on the African mainland, which is wedged into Senegal.

"Stop summary executions. The African Union and ECOWAS must react," read one banner, referring to the regional Economic Community of West African States. A handful of riot police kept close watch on the demonstration.

Two Senegalese were among nine prisoners shot by firing squad on Sunday night, a week after Jammeh vowed to execute all prisoners on death row by mid-September.

According to Amnesty International, another 38 prisoners are at "imminent risk" of execution.

"He has already executed some, he is threatening to execute more ... that is why we are here, to demand he reverse his decision," said Diene Ndiaye of Amnesty Senegal.

"We have information that he has become completely mad; it is that in fact, there is no explanation," he charged, urging the international community to investigate Jammeh's sanity as he "could pose a threat".

Several other rights workers and protesters said the actions of the 47-year-old former military officer, who also claims he can cure AIDS, could only be explained by "madness".

Mahawa Cham, a former Gambian lawmaker (2001-2006) and member of Jammeh's party, has no doubt that the president will continue his plans to execute the remaining prisoners.

"I believe he will continue to carry out the executions. This is a man who doesn't have sympathy for a human being. He thinks he is always right," Cham said.