By Kieran Guilbert

DAKAR, Oct 26 (Thomson Reuters Foundation) - Escalating violence in northern Cameroon combined with an influx of refugees from Nigeria and Central African Republic is placing immense strain on local communities already struggling to survive, the United Nations' aid chief said on Monday.

Cross-border raids and suicide bombings by suspected Boko Haram forces have uprooted more than 80,000 people in Cameroon's Far North region over the last year, the Office for the Coordination of Humanitarian Affairs (OCHA) says.

The region is also home to 60,000 Nigerian refugees who have fled attacks by the militant group since the start of 2013.

Boko Haram, which has waged a brutal six-year campaign to carve out an Islamist caliphate, used Cameroon's north to stockpile supplies and recruits until a government crackdown last year, but the militants have ramped up attacks this year.

"Entire communities have been uprooted from their homes... daily livelihood activities such as farming, trade, pastoralism and even movement are hampered by insecurity and increasingly frequent attacks and suicide bombings," U.N. humanitarian chief Stephen O'Brien told the Thomson Reuters Foundation.

He was speaking after a visit to Cameroon where food shortages and malnutrition have gripped the country's north with more than a million people not having enough to eat.

In eastern Cameroon, 250,000 refugees from Central African Republic are living with host communities, more than half having fled violence which has plagued the mostly Christian nation since Muslim Seleka rebels briefly seized power in March 2013.

Recent unrest in the capital Bangui, which killed dozens, injured hundreds and uprooted tens of thousands, ended hopes of holding elections scheduled for Oct. 18, leaving the refugees in eastern Cameroon unsure of when they may return home, OCHA said.

The number of refugees and Cameroonians displaced by violence in the country, more than 400,000 people in total, has quadrupled since the start of 2014, according to the U.N. body.

"Deprived and traumatized families fleeing violence in the Central African Republic and Nigeria are being hosted by impoverished but generous communities, themselves facing daily hardship," O'Brien said.

The trauma suffered by those displaced coupled with the growing pressure on local hosts could fuel tensions, he added.

"That risk exists... as more people seek refuge among communities struggling every day to feed themselves or access basic services, pressure on limited resources increases."

Almost two million people across Cameroon urgently need humanitarian aid, according to OCHA. The humanitarian appeal for the country - $264 million - has been 42 percent funded to date. (Reporting By Kieran Guilbert, Editing by Katie Nguyen; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit www.trust.org)