* Czechs, Romanians and Russians killed
* "So abrupt, and so sudden"
* Greek PM cancels meetings
* Winds exceeded 100 kph (Releads, adds Reuters witness, expert, wind intensity)
By Karolina Tagaris and Alkis Konstantinidis
ATHENS/NEA PLAYIA, Greece, July 11 (Reuters) - Six foreigners including two children were killed and more than 100 other people injured when a violent, short-lived storm lashed northern Greece overnight, felling trees and ripping off rooftops.
Witnesses reported the storm had come and gone in a matter of minutes. Winds of over 100 kph (60 mph) were reported on the Halkidiki peninsula, popular with tourists in the summer.
Two elderly Czech tourists were killed when strong winds and water overturned their travel trailer, police said.
A woman and an 8-year-old boy from Romania were killed when a roof collapsed on a restaurant in the beach resort of Nea Plagia. And a man and a young boy, both Russians, died when a tree fell near their hotel in the seaside town of Potidea, authorities said.
Streets in the area were dotted with uprooted pine trees and overturned motorcycles, and wooden rooftops had been torn off and dumped on beaches. A Reuters correspondent saw sun loungers strewn in mangled heaps with other debris across Nea Plagia's golden beaches.
Prime Minister Kyriakos Mitsotakis, whose government was sworn in this week after winning elections on July 7, cancelled his morning schedule and was being continuously briefed, a government official said.
Civil Protection Minister Mihalis Chrisochoidis, at the scene, said Greece was mourning the loss of life, adding: "In coming days all damage will be repaired."
Such severe storms are unusual in Greece, where summers are typically hot and dry. But the tragedy had echoes of a wildfire almost a year ago that raced through the resort of Mati almost without warning, fanned by hot winds, trapping many inhabitants before they could flee and killing 100 people.
"It is the first time in my 25-year career that I have lived through something like this," Athansios Kaltsas, director of the Nea Moudania Medical Centre, where many of the injured were treated for fractures, told Greek television.
"It was so abrupt, and so sudden."
Kaltsas said patients taken to the clinic ranged in age from 8 months to over 70. Some had head injuries from trees and other falling objects.
Authorities said around 100 people, mostly tourists, had been injured, and 23 of those had been admitted to hospital. There were widespread power cuts.
"Here we dealing with a new situation," geology and natural disasters expert Efthymios Lekkas told Skai TV. "Climate change is an accelerated and self-sustaining cycle that creates new hazards, with increased duration and intensity." (Additional reporting by Michele Kambas; Editing by Kevin Liffey)
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