"I had the honor of an audience with the president of the Nigerien transition, head of state General Abdourahamane Tiani," said Soro on X, formerly Twitter, adding he had met with other senior officials in a 90-minute exchange.
Soro said he had notably met General Salifou Mody, the defence minister, and General Mohamed Toumba, the interior minister, adding their exchanges were "exceptional in their quality and depth."
Earlier, Soro, sentenced to life in prison two years ago for undermining national security, said he had arrived in Niamey on Saturday, from where he announced Sunday he was ending four years of self-imposed exile in Europe and Dubai.
He was previously right-hand man to President Alassane Ouattara, but the pair fell out in 2019, with the head of state accusing him of fomenting a "civilian and military insurrection."
Soro then went into exile, and an Ivorian court sentenced him in absentia to life imprisonment in 2021.
"It needed a military government in Niger to allow me to tread my beloved ancestral land of Africa," Niger television quoted him as saying after the meeting.
On Sunday, he said it was too hard to live far from his native land and he was ending his exile.
"I refuse to be a fugitive. I am guilty of no crime," he said, adding he wanted to "contribute to the reconciliation" of the country's population, without specifying a return date.
"It's a well-worn adage. My enemy's enemy is my friend," said Ivorian political analyst Geoffroy Kouao. "Soro is choosing Niger because he knows current relations between Abidjan and Niamey are execrable."
Soro was head of an insurgency that controlled the northern half of Ivory Coast in the early 2000s.
He provided crucial military support to Ouattara in his tussle with the then president, Laurent Gbagbo, who was ousted in 2011 after a brutal post-election conflict.
Soro became Ouattara's first prime minister and in 2012 was named speaker of the National Assembly.
In April 2020, Soro was sentenced to 20 years' jail for handling embezzled public funds prior to his life term handed down the following year for endangering state security.
On Sunday, he said an attempted arrest against him was made at Istanbul airport on November 3, in a bid to extradite him to Ivory Coast.
Ouattara was one of several western African leaders who spoke out against the July 26 Niger coup and in favor of a military intervention as proposed by West African bloc ECOWAS, which imposed sanctions in an attempt to have ousted Nigerien president Mohamed Bazoum reinstated.
Former Ivoirian Prime Minister Says He Met with Niger Military Leader
FILE — Former Ivory Coast Prime Minister and Presidential candidate Guillaume Soro holds a press conference on September 17, 2020 at the Bristol Hotel in Paris.
NIAMEY - Former Ivorian prime minister Guillaume Soro said Monday he had had extensive talks with Niger's putsch leaders in Niamey, a day after announcing he was ending years of self-imposed exile.