Iceland raised the alarm after its largest volcano was hit by the biggest tremors since 1977.

Two quakes larger than four in magnitude early Monday rocked the crater of Katla, the country’s Met Office said in a statement.

That was followed by at least 10 more tremors at the volcano, which rises 1,450 metres (4,757 feet) into the air on the North Atlantic island’s southern coast. There were no immediate reports of casualties or damages to property.

Katla last erupted in 1955 and 1999. Neither of those were large enough to break the ice covering its ten kilometre-wide (six mile) caldera.

Its last major eruption was back in 1918, when it spewed ash for more than five weeks.

Hawaii’s spectacular ‘smiley’ volcano

An eruption of the Eyjafjallajokull volcano in 2010 caused the cancellation of more than 100,000 flights across Europe on concern that glass-like particles formed from lava might melt in aircraft engines and clog turbines.

Volcanic ash cloud from Iceland grounds all UK flights Show all 11 1 /11 Volcanic ash cloud from Iceland grounds all UK flights Volcanic ash cloud from Iceland grounds all UK flights Spectacular pictures taken from a helicopter at sunset on April 14, 2010 show how ash from an Icelandic volcano is severely disrupting travel plans for British air passengers MARCO FULLE / BARCROFT MEDIA LTD Volcanic ash cloud from Iceland grounds all UK flights Spectacular pictures taken from a helicopter at sunset on April 14, 2010 show how ash from an Icelandic volcano is severely disrupting travel plans for British air passengers MARCO FULLE / BARCROFT MEDIA LTD Volcanic ash cloud from Iceland grounds all UK flights Spectacular pictures taken from a helicopter at sunset on April 14, 2010 show how ash from an Icelandic volcano is severely disrupting travel plans for British air passengers MARCO FULLE / BARCROFT MEDIA LTD Volcanic ash cloud from Iceland grounds all UK flights Lava, smoke and ash billowing from the Fimmvorduhals volcano near the Eyjafjallajokull glacier HALLDOR KOLBEINS/AFP/Getty Images Volcanic ash cloud from Iceland grounds all UK flights Smoke and ash billows through the clouds yesterday above the volcano in Eyjafjallajokull REUTERS/Ingolfur Juliusson Volcanic ash cloud from Iceland grounds all UK flights Lava, smoke and ash billowing from the Fimmvorduhals volcano near the Eyjafjallajokull glacier HALLDOR KOLBEINS/AFP/Getty Images Volcanic ash cloud from Iceland grounds all UK flights A cloud of volcanic ash is seen between Iceland (TOP L) and Scotland, in northern Britain, in this handout satellite photograph taken at 0800 GMT on Thursday, and received from Britain's Met Office in London on April 15, 2010. Airport operator BAA said on Thursday it expected all flights in and out of London's Heathrow and Stansted airports to be suspended from 12:00 p.m. due to a cloud of volcanic ash from an eruption in Iceland. Reuters Volcanic ash cloud from Iceland grounds all UK flights Passengers face disruption at Manchester Airport after all flights were grounded due to volcanic ash on April 15, 2010 in Manchester, England. Getty Images Volcanic ash cloud from Iceland grounds all UK flights An airline passenger rests on the floor as he waits for a flight at Manchester Airport in north-west England on April 15 2010, after the airport was closed following a cloud of volcanic ash from an eruption in Iceland. No flights will be allowed into British airspace from 1100 GMT until at least 1700 GMT Thursday due to an ash cloud from a volcanic eruption in Iceland, air traffic control services announced. AFP Volcanic ash cloud from Iceland grounds all UK flights Passengers face disruption at Glasgow airport after all flights were grounded due to volcanic ash on April 15, 2010 in Glasgow, Scotland. All flights in and out of Scotland's airports have been grounded due to a plume of volcanic ash drifting across northern Europe from an eruption in Iceland. Getty Images Volcanic ash cloud from Iceland grounds all UK flights Aircraft are pictured parked on the apron at Manchester Airport in north-west England, on April 15, 2010, following the closure of the airport due to a cloud of volcanic ash from Iceland. All London flights, including those from Heathrow, will be suspended from 1100 GMT Thursday due to volcanic ash from Iceland that has already caused almost 300 cancellations here, officials said. "All flights in and out of Heathrow and Stansted will be suspended from midday but the terminals will remain open," a spokeswoman for airports operator BAA told AFP. AFP

Historically, Eyjafjallajokull has been known to erupt one to two years prior to Katla.

A magnitude 6.2 quake killed at least 250 people in central Italy last week.