* Six children wounded in attack in Delta state
* Islamist Christmas bombs could foment sectarian strife
* President Jonathan hints at security reshuffle
* Separate attack in Plateau state underscores fragility
By Austin Ekeinde and Tife Owolabi
PORT HARCOURT/JOS, Dec 28 (Reuters) - Assailants threw a homemade bomb into a madrassa in southern Nigeria's Delta state, police said, wounding seven people and escalating tensions between Muslims and Christians after a spate of church bombings across the nation.
Six of the wounded were children younger than nine learning the Koran at the Islamic seminary, or madrassa.
In a separate incident, armed Fulani herdsmen shot dead three members of a family in the ethnically and religiously mixed Plateau state on Wednesday, witnesses and officials said. .
The school attack on Tuesday night came two days after Christmas Day bombings of churches and other targets by Islamist militant group Boko Haram killed 32 people in a coordinated strike that seemed aimed at igniting sectarian strife.
"Some men driving in a Camry car threw a low-capacity explosive into a building where an Arabic class was taking place," police spokesman Charles Muka said.
"Children aged between four and nine were taking a lesson. Six children were injured and one adult," he said.
He said police suspected a local vigilante group.
Boko Haram, a sect which aims to impose Islamic sharia law across Nigeria, claimed responsibility for the Dec. 25 attacks, the second Christmas in a row it has caused carnage.
The worst attack killed at least 27 people in the St Theresa Catholic church in Madalla, a town on the edge of the capital Abuja, and devastated surrounding buildings and cars as worshippers poured out of the church after Christmas mass.
The attacks risk reviving sectarian violence between the mostly Muslim north and Christian south, which has killed thousands of people in the past decade.
Speaking at a meeting with President Goodluck Jonathan on Wednesday, Ayo Oritsejafor, head of the Christian Association of Nigeria (CAN), an umbrella group for all denominations, said Christians had become victims of "Islamic Jihad".
"It is considered as a declaration of war on Christians and Nigeria," Oritsejafor said. "CAN has found the responses of ... Islamic bodies on this matter to be unacceptable and an abdication of their responsibilities."
"The Christian Community is fast losing confidence in government's ability to protect our rights."
Jonathan promised to do more to tackle the threat of Islamists and hinted at a reshuffle in his security services.
"We will restructure ... and make sure we get a team that will meet with the challenge we are facing today," he said. "I will plead with religious leaders, both Muslim and Christian leaders, to work together."
Nigerian Christians fear the Christmas Day bombings could lead to a religious war in Africa's most populous country.
There was no suggestion the killings in Plateau had any link to Sunday's church bombings, as the victims were Christians.
The state is a tinderbox of ethnic and religious rivalries over land and power between local people and migrants from other areas that often take the form of sectarian strife between the state's Christian and Muslim communities.
Women wept and wailed in anguish over the bodies of a husband and wife in their thirties and their baby child, all of which were riddled with bullet holes.
"When the Fulani herdsmen came around late in the night, I managed to escape through the window before they killed my son, daughter-in-law and grand-daughter with guns," said Mary Pam, the mother of Philip Francis, one of the victims. (Additional reporting by Felix Onuah in Abuja and Anamesere Igboeroteonwu in Onitsha; Writing by Tim Cocks; Editing by Myra MacDonald and Matthew Jones)