* Gunmen set off bombs, fire on congregation
* Islamist Boko Haram often target Christians
* Nigerian forces are struggling to contain insurgency (Updates death toll from second attack)
By Imma Ande
YOLA, Nigeria, Jan 27 (Reuters) - Suspected insurgents armed with guns and explosives killed at least 62 people in northeast Nigeria, including at a church service, in a region where Islamist sect Boko Haram is resisting a military crackdown, witnesses said on Monday.
They killed 22 people by setting off bombs and firing into the congregation in the Catholic church in Waga Chakawa village in Adamawa state on Sunday, before burning houses and taking residents hostage during a four-hour siege, witnesses said.
On Monday, a separate assault by suspected members of the shady sect killed at least 40 people in Kawuri village, in remote northeastern Borno state, security officials said. No one immediately claimed responsibility for either attack.
President Goodluck Jonathan is struggling to contain Boko Haram in remote rural regions in the country's northeast corner, where the sect launched an uprising in 2009.
Boko Haram, which wants to impose sharia law on a country split roughly equally between Christians and Muslims, has killed thousands over the past four and a half years and is considered the biggest security risk in Africa's top oil exporter and second largest economy after South Africa.
Its fighters' favourite targets have traditionally been security forces, politicians who oppose them and Christian minorities in the largely Muslim north.
The spokesman for the Catholic Diocese of Yola, Reverend Father Raymond Danbouye, confirmed 22 people killed in the church were buried at a funeral on Monday.
The military and police did not respond to requests for comment but one army source confirmed the church attack, asking not to be named because he wasn't authorised to speak with the media.
Waga Chakawa is near the border with Borno state, in which the second attack occurred that killed at least 40 people.
Several witnesses put the figure at 50, although none had counted the numbers of bodies themselves. They added that the militants had burned down the village and set off multiple explosions, shooting anyone trying to flee.
"The whole village has been razed by Boko Haram and there were still loud explosions from different directions as I left, with bodies littering the village," said resident Bulama Kuliri, who narrowly escaped.
An army spokesman did not immediately respond to a request for comment.
Jonathan replaced his chiefs of defence, army, navy and air force last week in a widespread military shake-up. No reason was given for the overhaul, but security experts believe there was a need for a change of tactics in combating Boko Haram.
Jonathan declared a state of emergency in three northeastern states in May last year and launched an intensified military campaign to try to end the insurgency. (Reporting by Imma Ande; Writing by Joe Brock; Editing by Tim Cocks and Alister Doyle)