West African leaders have abandoned a trip to discuss Togo's constitutional crisis, and threatened to suspend the country from regional grouping Ecowas.
The Togo opposition does not recognise the new leader
Togo had tried to divert the talks from the capital Lome to a northern city.
The heads of state, meeting in Benin, demanded that the new Togolese leadership attend talks in Niger on Saturday or face immediate sanctions.
In Lome, riot police dispersed hundreds of opposition supporters, protesting at the weekend's "military coup".
Earlier, regional heavyweight Nigeria said it was recalling its ambassador.
The constitutional amendment which allowed Faure Gnassingbe to be installed as president following the death of his father Gnassingbe Eyadema has been condemned by West African leaders, and the international community.
On Friday, South Africa's President Thabo Mbeki described it as "a charade".
Togo wanted the leaders of Benin, Ghana, Mali, Niger and Nigeria to travel to the northern city of Kara, near the home area of new leader Faure Gnassingbe instead of the capital.
But the heads of state cancelled the trip after a Nigerian advance party was refused permission to land in Lome, and called a meeting in the Niger capital Niamey instead.
"If they do not attend tomorrow, Ecowas sanctions will apply automatically and immediately," said the grouping's spokesman, Mohammed ibn Chambas.
He added that the sanctions would mean immediate suspension at all levels.
"They will not be able to participate in Ecowas activities until the constitutional process has been put on track," Mr Chambas said.
BBC Africa analyst Elizabeth Blunt says the proposed change of venue to Kara would have been significant because it is close to the Gnassingbe family's home village, where Eyadema's body has been taken.
A Nigerian spokeswoman said that Mr Obasanjo's advance party had been refused entry to Togo, but Togolese Information Minister Pitang Tchalla said their flight had merely been diverted to Kara.
Togo's transfer of power has been condemned as a coup
Mr Chambas said Lome had been asked to "apologise unreservedly" to Mr Obasanjo for the incident.
Nigeria has also restricted the movements of Togolese diplomats and has warned its tiny neighbour that it would be held responsible for any violence against the many Nigerians who live in Togo.
The leaders met in the Benin capital, Cotonou, before deciding not to travel to Kara.
They also met Togo's former speaker of parliament Fambare Natchaba Ouattara, who was supposed to succeed Eyadema before the constitution was hastily amended.
The Lome demonstrators set fire to tyres, sending thick plumes of black smoke into the air above the opposition stronghold of Be.
"We know how to shoot guns and we are ready to fight," said Kofi Awokou, a 30-year-old mechanic.