Tensions in Chad are rising on all fronts

Bit by bit, tensions in Chad are rising again. In recent weeks, a French civilian airplane suffered a terrorist bombing, and nine French soldiers were killed when a mine exploded while they were on patrol.

At the same time, friction has emerged on the home turfs of the two rivals for power. In the south, Muslim President Hissein Habre is facing opposition from the area's Roman Catholics, including sporadic attacks on government forces.

In the north, former President Goukhouni Woddei's rebels seem increasingly dissatisfied with their Libyan allies. Recent reports from N'Djamena - Habre's capital - say the rebels even battled with Libyan troops, leaving up to 50 dead. This may be an exaggeration designed to discredit the rebels, but French sources indicate Woddei has sent diplomatic signals that he wants to assert his independence and abandon Tripoli as his headquarters.

None of these developments foreshadows a diplomatic breakthrough - or imminent full-scale war. But the risks are rising on all sides.

Libya has reinforced its positions in northern Chad and Woddei's rebels are slowly being pushed aside. There is not much they can do to keep from being swallowed up by the Libyans.

''Goukhouni is dependent on the Libyans,'' a French official says. ''He has no other potential partner.''

Habre, too, is being squeezed. His preoccupation with troubles in the south has weakened his negotiating position on ending the war with Woddei. He is increasingly dependent on the 3,000 or so French troops protecting his northern flank. He also becomes a more uncertain ally for the French.

Meanwhile, the French are becoming more uncomfortable.

Officials deny a French pullout is under consideration. They insist the soldiers have effectively stopped the Libyan-rebel advance, possibly opening the way for negotiations.

But the attack on the civilian plane and the death of the nine soldiers has shaken France a bit. At first, French officials said the soldiers were killed while trying to defuse a mine. Then rebels claimed they killed the soldiers in an attack. Defense Minister Charles Hernu ordered an investigation.

Defense Ministry officials acknowledge that the incident may signal a new danger for the French forces - a terror campaign designed to weaken French will.

This statement and the realization that French troops may be in Chad much longer have stirred press criticism.