France, March 10 -- The death of Yaya Dillo - the main rival to transitional Chadian president Mahamat Idriss Deby in upcoming elections in May- has deepened the political strife plaguing the country.

The European Union and Human Rights Watchhave called for aninternational investigation into Dillo's death, which his party has labelled an assassination.

During a visit to Paris last Tuesday, Chadian Prime Minister Succes Masra said he had agreed to the probe.

Presidential elections in May and June are meant to assure the return of constitutional rule to Chad, three years after military authorities seized power in a coup led by Deby.

However, Dillo's killing during a shoot-out at his party's headquarters last week has thrown a dark shado...