An erupting volcano in the Canary Islands has turned “much more aggressive”, officials have warned, after two further cracks blew open, spewing lava.

Amid reports of “intense” activity on La Palma, the fresh fissures, some 25m (50ft) apart, sent scorching rivers of molten rock down towards the sea, parallel to an earlier flow that reached the Atlantic Ocean earlier this week.

Nearly two weeks after it erupted, the volcano is “much more aggressive,” said Miguel Angel Morcuende, technical director of the Canary Islands’ emergency response department.

Overnight, scientists recorded eight new earthquakes up to a magnitude of 3.5.

The eruption was sending gas and ash up to nearly four miles (6km) into the air, officials said.

The evacuation of more than 6,000 people since last month’s eruption has helped prevent casualties.

An area of solidified lava where the molten rock is flowing into the sea now extends over more than 50 acres (20 hectares).

Officials have been monitoring air quality along the shoreline and although sulphur dioxide levels in the area had increased, it did not represent a health threat, La Palma’s government said.

However, it advised local residents to stay indoors and people on the island wear face masks and eye protection to guard against volcanic ash.

The volcano has so far belched some 80 million cubic metres of molten rock, scientists estimate – more than double the amount in the island’s last eruption in 1971.

The lava has so far destroyed or damaged more than 1,000 properties, including homes and farm buildings, and smothered around 1,750 acres (709 hectares) of land.

Follow the Daily podcast on Apple Podcasts, Google Podcasts, Spotify, Spreaker

La Palma, which is home to around 85,000 people who mainly earn their living from fruit farming and tourism, is around 22 miles (35km) long and 12 miles (20km) wide at its broadest point.

It is part of the volcanic Canary Islands, an archipelago off northwest Africa that is part of Spanish territory.