Chadian rebels have entered the capital city N'Djamena after intense fighting with government forces.
The government has denied claims the city has fallen.
President Idriss Deby Itno is reported to be holed up in the presidential palace but a Chadian rebel leader said he can leave his palace if he so wishes.
'We control the situation, we control the city, there are some pockets of resistance,' rebel Abakar Tollimi said.
France said it 'strongly condemns the attempt to seize power' in Chad by 'armed groups from the outside.'
It called for 'peace and reconciliation' and expressed support for mediation launched earlier tpday by the African Union.
An army spokesman here said a small advance party of Irish soldiers in Chad are safe.
A decision in regard to the deployment of Irish troops will be taken on the basis of events over the coming 48 hours.
Despite the reports, Chad's foreign minister said Mr Deby was at the presidency and the situation was under control in the city.
Heavy fighting between some 2,000 rebels opposed to Mr Deby and government forces raged in the capital today.
The rebels entered the capital in trucks armed with machine guns, rocket launchers and Kalashnikov assault rifles.
Intense firing during the morning died down by midday but a column of black smoke was seen rising from near the presidential palace.
France announced that a combat unit of 150 extra troops had arrived in Chad. French forces have been assisting the government with logistics and intelligence but have not been allowed to intervene militarily in the fighting.
A spokesman for French President Nicolas Sarkozy said he had a 'long conversation' with Mr Deby, and held an emergency meeting on the situation.
France also warned its nationals located there to remain indoors and prepared to evacuate them.
The country has 1,500 citizens in Chad, a former French colony, with 85% of them in the capital.
UN agencies try to evacuate staff
The United Nations is trying to evacuate more of its staff from the Chadian capital, a spokesman for the UN refugee agency said today.
The spokesman said it is planned to evacuate 51 UN staffers to Cameroon, including nine employees of the UN High Commissioner for Refugees (UNHCR), which is based in Geneva.
However, the UN had received no authorisation to fly an aircraft into Ndjamena and the world body was trying "other means" to bring its people out, he said.
"The situation does not allow the UN to do its job for the time being," the spokesman said, adding that it was "temporary decision."
The United Nations said Friday it had already evacuated 'non-essential' personnel from Ndjamena.
The spokesman said most UNHCR employees in Chad were in refugee camps in the east of the country, where the situation was still calm.
