UPDATE 5-Nicaragua's Ortega headed back to power, blow to US

(Adds new results; comments from Ortega, Cuba's Lage)

By Kieran Murray and Catherine Bremer

MANAGUA, Nicaragua, Nov 6 (Reuters) - Former Marxist revolutionary Daniel Ortega was headed back to power on Monday in a presidential election 16 years after Nicaragua's voters ousted him to end a brutal civil war with U.S.-trained Contra rebels.

Ortega's almost certain victory was a blow to Washington and reinforces an anti-U.S. alliance in Latin America led by Venezuelan President Hugo Chavez.