GUWAHATI, India, Feb. 24 (Reuters) - At least 14 policemen were killed on Saturday in an ambush by suspected militants in India's remote northeastern state of Manipur, a day after provincial elections were held there, a police officer said. Personnel of the India Reserve Battalion were patrolling in a vehicle in the mountaineous district of Tamenglong, about 85 km (50 miles) northwest of the state capital, Imphal, when grenades were thrown at them and they came under fire. "Twelve people died on the spot and two others succumbed to their injuries later," the officer, who declined to be indentified, told Reuters by telephone. Manipur is plagued by a decades-old insurgency seeking a separate homeland for its ethnic and tribal population.