Thirteen Egyptian Coptic Christians seized in Libya over the weekend in the coastal city of Sirte have been freed, an official says.

A tribal leader said that the Copts had been detained by people smugglers.

The head of the council of elders in Sirte told BBC News that the Egyptians were released by their captors on January 5 after local officials began negotiating with the gunmen.

"The Egyptians were held by a group that deals in illegal people smuggling, because of a dispute involving money and transportation to the Harawa region east of Sirte," Muftah Marzuq told reporters.

The disappearance of the Egyptian workers in Sirte surfaced after a source close to the government accused the Islamist group Ansar al-Sharia of having a hand in the purported kidnapping.

The incident came after another incident where seven other Coptic Christians from Egypt were allegedly abducted at a fake checkpoint in Sirte while trying to leave the city.

Marzuq did not say anything about the earlier kidnapping.

On January 3, eyewitnesses said gunmen stormed a residential compound in Sirte and combed through the complex in the middle of the night. They read from a list of names and took away the Christians living in the compound.

Some residents said the masked gunmen separated Christians from Muslims, before handcuffing the Copts and taking them away in cars.

The incident was the latest in a series of attacks on Egyptian Christians working in Libya.

In early December, an Egyptian Coptic doctor and his wife living in Sirte were killed inside their house. The couple's daughter was also killed after being kidnapped, according to local reports.

Instability has plagued country since the dictator Muammar Gaddafi was deposed in 2011.

Libya hosts a large community of both Muslim and Coptic Egyptians, most of whom are working in the construction sector.