At least 18 people, thought to be illegal migrants in hiding, were reported killed as Greece battled to contain several raging wildfires across the country on Wednesday.

A fire ripped through the foothills of Mount Parnitha, the largest forest adjoining the capital, and is threatening to spread to its national park.

The Greek capital woke up Wednesday to the smell of scorched earth and thick black smoke covering the sky.

Fires have already destroyed homes and properties in the nearby suburb of Hasia and Fyli and are threatening the suburb of Menidi.

"Unfortunately, the wind does not help at all," Stathis Topalidis, deputy mayor of Menidi told state TV ERT.

On Tuesday, authorities ordered the evacuation of Ano Liosia in northwest Athens, a district of over 25,000 people, even though several stayed at their houses trying to protect their properties.

Another big blaze was still raging at a landfill in the industrial zone of Aspropyrgos, west of Athens.

Flames continued to spread unchecked for a fifth day in the northeastern region of Evros, close to the Turkish borders and in Alexandroupolis and the Dadia forest, home to rare birds of prey.

More evacuations were ordered in the region overnight.

Fateful journey

Earlier Tuesday, 18 suspected migrants were found dead in a forest fire north of the northeastern port city of Alexandroupolis.

The dead included two children, a police official said.

As no local residents had been reported missing "the possibility that they are people who entered our country illegally is under investigation," fire department spokesman Yiannis Artopios said in a televised address.

Blazes were also raging on the islands of Evia and Kythnos, the region of Boeotia, north of Athens and in western Greece.

Another fire that broke out Tuesday on the island of Samothraki was contained overnight, but the island remains without electricity.

Over 40,000 hectares (nearly 99,000 acres) were destroyed in wildfires in just three days from Aug. 19 to 21, according to a report by the National Observatory of Athens.

The very hot and dry conditions which increase the fire risk will persist until Friday, according to meteorologists.

Nearly 20,000 people were evacuated from the Greek island of Rhodes as massive wildfires forced the country's largest-ever fire evacuation late July.