He said that France, Chad's former colonial ruler, "must get involved in the crisis" and that "all protagonists must meet at a conference".
"We plan to carry the war to the interior of the country," he said.
Koulamallah, whose Democratic Union for Change (UDC) group belongs to Chad's rebel alliance, said the fighters had come under attack from government helicopters and had fired back, hitting a helicopter.
A clash in the area was confirmed by the EU force (Eufor), which is deployed to protect refugees, civilians and aid workers in eastern Chad, including the Dar Sila region, where UN-run camps are located.
President Idriss Deby seized power in a Libyan-backed coup in 1990
He went on to win the Chad's first two
multi-party elections in 1996 and 2001
A ceasefire signed between Deby and four rebel groups in October recently collapsed
The largest rebel group, the Union of Forces for Democracy and Development, is led by a former minister who accuses Deby of corruption
In February, several hundered people were killed when Chadian rebels attacked Ndjamena
Click here for more on Chad's spiral into conflict
Irish Eufor troops based at Goz-Beida in the Dar Sila region said they had received reports of a clash at Modeina, 70km northeast of Goz-Beida.
"The action is between the UFDD [a rebel group which is part of the National Alliance] and the Chadian air force but we have no details on casualties or damage," Commandant Stephen Morgan, spokesman for the Irish 97th infantry battalion, said.
"We have no assets in the area ourselves so we can not confirm these reports first hand."
Reports from the AFP news agency said that one of the a Chadian air force helicopters made a forced landing after taking part in an attack on rebel positions near the Sudan border.
Two Russian-made Mi-35 attack helicopters and a larger, armed Mi-17 transport helicopter had set off from Abeche, the main city in the east of Chad to target rebels in the area of Moudeina and Ade, an AFP source said.
Upon returning to Abeche, one of the helicopters made "a hard and forced landing" at the airport, about 500 metres from the Eufor camp.
There were no reported casualties in the incident that happened around 9.05am (08:05 GMT).
Ali Gueddei, a spokesman for the National Alliance speaking from Gabon's capital of Libreville, said that his fighters had "shot down a helicopter".
He also said that the rebel advance on Ndjamena was "imminent".
In February, Chadian rebels attacked the captal, besieging Deby in his palace. Several hundred people were killed in the fighting.
The rebels later withdrew from the capital after the government and French troops came out in support of the president, who himself seized power in a revolt in 1990.