ATHENS, Greece -- Hundreds of firefighters battled wildfires in Greece Tuesday, with the largest burning through a thickly forested nature reserve on the island of Evia north of Athens where four villages and a monastery were evacuated.

The country's civil protection authority declared a state of emergency in the area of Evia affected by the fire, where more than 220 firefighters, volunteers, soldiers, six water-dropping planes and six helicopters were deployed, along with one more helicopter co-ordinating the air support.

Greece called on the European civil protection organization for assistance, and firefighting planes were being sent from Croatia and Italy, the Greek protection authority said.

Prime Minister Kyriakos Mitsotakis cut short his vacation on the southern island of Crete and returned to Athens, his office said. He was to head to the fire department's command centre Tuesday afternoon.

Smoke from the fire blanketed the Greek capital in the morning. Authorities warned people in affected areas, particularly the elderly, young children and those suffering from breathing or heart conditions, to remain indoors and set air conditioning units to recycle indoor air.

The fire broke out shortly after 3 a.m. local time, the civil protection authority said, and was fanned by strong winds that spread it through the dense pine forest.

A separate blaze broke out on the north part of Evia, and 15 firefighters, a helicopter and a small plane worked to keep it from spreading.

Dozens more firefighters, two planes and a helicopter tackled a separate forest fire on the northern island of Thassos. Another wildfire was burning through brush and dried weeds near Thebes, northwest of Athens. More than 30 firefighters tackled yet another in southern Greece, which the fire department said was brought under partial control after about an hour.

Forest fires are common in Greece during the hot, dry summer months. Authorities have repeatedly warned the public not to engage in outdoor activities that could cause fires, such as welding work, burning dried weeds or lighting campfires and barbecues. Parks and forest areas are closed to the public at times of high fire risk.

Last year, more than 100 people died when a fast-moving forest fire broke out in a seaside area northeast of Athens and raged through a nearby settlement of mainly holiday homes. The fire trapped people in their cars as they attempted to flee, while many other victims drowned as they tried to swim away from beaches overcome by heat and choking smoke.