Attackers threw a homemade bomb at an administration building belonging to the Egyptian Coptic church in Dafniya, close to the western city of Misrata, said Ibrahim Rajab of the Misrata military council.
The Egyptian consul in the city, Tareq Dahrouj, said he visited the church and the building where the two church workers were killed early on Sunday.
"The explosion seems like it was very strong and I have started making my investigations with Misrata officials,'' he said.Libya has small communities of Egyptians, Greeks and Italians who account for most of the Christian minority in the predominantly Islamic country.
Libya's new rulers have struggled to impose their authority on myriad armed groups who helped oust dictator Moammar Gadhafi last year but have yet to lay down their arms. Sunday's attack was the first major assault on a Christian target since the revolution.
Coptic Christians in Egypt have become increasingly worried after an upsurge in attacks on churches, which they blame on hardline Islamists, in the wake of the removal from office in 2011 of President Hosni Mubarak.
Repeated attacks on foreign diplomatic and aid centers in Libya's eastern city of Benghazi have made it very dangerous for non-locals to work and live there.
The worst attack on a foreign target was on Sept. 11, when the U.S. Ambassador Chris Stevens and three embassy staff were killed in an attack on the U.S. mission in Benghazi.
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