Media playback is unsupported on your device Media caption The BBC's Jon Donnison: "People are worried the whole side of the mountain could slip down"

Heavy rain and floods are affecting dozens of villages, after Typhoon Koppu swept through the northern Philippines.

The slow-moving weather system has killed at least two people and forced tens of thousands from their homes.

Troops have been deployed to help residents trapped on rooftops, but are struggling to access more remote areas.

Koppu has now been downgraded to a severe tropical storm by the Japanese Meteorological Agency, which is responsible for naming and tracking it.

However, the Philippines' own weather agency, which calls the weather system Lando, is still characterising it as a typhoon.

Despite weakening, Koppu is expected to keep dumping rain on the country for a considerable time to come. Some forecasts suggest it may not be until Wednesday that it moves past the Philippines and on to Taiwan.

Image copyright EPA Image caption With rains still falling, the risk of flooding is even greater than during typical storms and typhoons

At the scene: Jon Donnison, BBC News, Luzon, Philippines

Unlike previous tropical cyclones, the threat from typhoon Koppu is not so much from the wind but from the massive amount of rain.

More than a metre of rainfall is forecast in just a few days in Luzon province. That is double what London gets in an entire year.

In the south of Luzon, it has brought severe flooding with whole villages under water. But perhaps more dangerous are massive landslides. The fear is that with the ground heavy and saturated with water, whole hillsides could collapse.

We visited one small community near Burgos where 70 families are now living in a makeshift evacuation centre because of the fear the hills on which they live could collapse.

Typhoon Koppu made landfall near the town of Casiguran on the main island of Luzon on Sunday morning, bringing winds of close to 200km/h (124mph) and cutting power to vast areas.

A teenager was killed by a fallen tree in Manila which also injured four others. A concrete wall also collapsed in the town of Subic, northwest of Manila, killing a 62-year-old woman, officials said.

By dawn on Monday, wind speeds were down to 150 km/h (93 mph) in the northern town of Santiago, according to the state weather service.

But floodwaters are preventing even military vehicles reaching many of the worst-hit villages, and rescuers report a shortage of boats.

"We haven't reached many areas. About 60% to 70% of our town is flooded, some as deep as three metres," said Henry Velarde, vice mayor of Jaen, a town in Nueva Ecija province.

"There are about 20,000 residents in isolated areas that need food and water."

Media playback is unsupported on your device Media caption The BBC's David Shukman on Luzon: ''The sheer quantity of rain is what the authorities are really worried about''

While the Philippines is no stranger to typhoons and tropical storms, the slow-moving nature of Koppu means heavy rain will fall for longer than usual, bringing greater risk of flooding and landslides.

It is the second strongest storm to hit the archipelago this year.

Image copyright AFP Image caption Residents have been forced onto the roofs of their homes as floodwaters show no signs of abating

Image copyright EPA Image caption Essential supplies are being distributed at evacuation centres around the country

Justin Morgan, Philippines country director for the charity Oxfam, told the BBC while evacuations for those still in the path of the typhoon was the most urgent task, "we can expect that there will be needs in terms of helping people recover their livelihoods as we know that many of the farmers would have lost their crops".

Why is Koppu slow-moving? Chris Fawkes, BBC Weather Centre, explains:

There are two typhoons in the west Pacific at the moment - Typhoon Champi sits just to the east of Koppu.

The complex interaction between these two typhoons and the warm air within these storms helps to build a ridge of high pressure over Taiwan this weekend. It is this ridge that effectively traps typhoon Koppu over the Philippines for a number of days rather than it being able to turn away from the Philippines and out of harm's way to the South China Sea.

Media playback is unsupported on your device Media caption Peter Gibbs looks at severe flooding and rain in Luzon - and more on the way

In a different storm in the central Philippines, a passenger boat with 41 people on board has capsized, leaving seven dead and two missing, the coast guard said.

The accident is said to have happened as the boat was travelling to Guimaras province.

In 2013, Typhoon Haiyan tore through the Philippines causing major destruction and leaving more than 7,300 people dead or missing.

Image copyright AP Image caption As the storm whipped up seas near Manila, one man took the chance to scavenge for recyclable materials

Are you in the Philippines? You can share your experiences by emailing haveyoursay@bbc.co.uk with your comments if it is safe to do so.

Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways: