ABUJA, Nigeria — Fleeing residents say scores of Boko Haram extremists are advancing on Nigeria's northeastern city of Bauchi and soldiers are engaging them with heavy gunfire. Fighter jets flew above the city.

The fighting comes as Nigerians continue to vote in some areas in a critical presidential election that the extremists have threatened to disrupt.

Police spokesman Haruna Muhammad says "unidentified gunmen" struck early Sunday, attacking polling stations in Kirfi and Alkaleri towns some 120 kilometers (75 miles) east of Bauchi.

By 2 p.m. residents said the extremists reached Dindima village 10 kilometers (6 miles) from Bauchi. Muhammad said the gunmen are in a convoy of 10 vehicles and security forces have stopped them at Dindima.

Boko Haram killed more than 40 people in attacks in three states on election day Saturday.