Nigerian pastor TB Joshua will host a New Year's memorial service for the South African relatives of those killed in a building collapse at his Lagos megachurch.

A spokesman at Joshua's Synagogue Church of All Nations (SCOAN) said 44 South Africans have flown to Lagos to attend the ceremony following the September disaster which killed 116 people, including 81 South Africans.

Joshua, a self-proclaimed prophet, "is going to lead the service to commiserate and offer spiritual support," said SCOAN spokesman Patrick Iwelumor.

"As the chief mourner, there is a need for (Joshua) to connect with these people," he added.

Joshua is one Nigeria's most influential and wealthiest pastors whose followers include prominent politicians and business leaders from across Africa and around the world.

The Lagos state coroner is carrying out an inquest into the causes of the collapse at a guesthouse within the church's compound.

Expert witnesses have said the structure was unsound and lacked proper permits, but Joshua's vocal followers have insisted the building came down as a result of foul play and was a bid to destroy the powerful religious leader.

Among the theories advanced by Joshua loyalists is that a plane flying in the area at the time of the collapse dropped an explosive device on the building.

One weapons expert called by SCOAN lawyers, Beidomu Iguniwei, has testified that the collapse could have been caused by an "infrasonic weapon," although there appears to be no credible evidence to support that claim.

Testimony at the inquest has dismissed sabotage as a cause, including evidence from aviation officials who said that the air force plane in question was on a routine training mission and had in fact landed before the building collapsed.

Joshua has refused to honour a series of summons demanding his appearance at the inquest. Some of his supporters have suggested it would be inappropriate for a so-called "Man of God" to be subjected to questioning.

Wednesday's candle light ceremony will begin at sundown and last through midnight, Iwelumor said.

The victim's relatives arrived in Nigeria on Christmas Day and Joshua is said to have paid for their travel.

When the trip was announced earlier this month, some South Africans took to social media to condemn Joshua's move as a bribe aimed at discouraging relatives from filing a lawsuit over the deaths.

But SCOAN's South Africa based spokesman, Kirsten Nematandani, has said the trip and New Year's memorial service are about "the spirit of caring".