An unidentified victim (C) of the Christmas day bombing of a church recovers at a hospital in Nigeria's capital Abuja, December 27, 2011. [Photo/Agencies]

PARIS - French President Nicolas Sarkozy on Tuesday vowed to support Nigeria in the fighting against terrorists following a spate of violent attacks on Christmas Day that killed over 40 people.

In a letter released by Elysee Palace, the French president strongly condemned the terrorist attacks in the northern city of Madalla "where a cowardly attack was directed against the Church of St. Theresa, while the Christmas Mass was celebrated there."

"In this symbolic day, terrorists have killed those who prayed for peace in the world," he added.

Sarkozy expressed "the friendship and solidarity of France" to the entire Nigerian people in the letter addressed to his Nigerian counterpart President Goodluck Jonathan, saying "these heinous crimes will strengthen our common determination to fight relentlessly against terrorism."

Nigeria is France's biggest trading partner in sub-Saharan Africa with French oil giant Total among the major producers of crude in the country.

At least 40 people were killed on Christmas Day after five bombing attacks targeted churches across Nigera. Islamist militant from Boko Haram group claimed the responsibility of the attacks.