Thousands of people in the west of Scotland are to spend a fourth night without power after it emerged that two electricity pylons were toppled by sheets of ice and snow.

Scottish and Southern Energy (SSE) said tonight that 3,300 customers in Kintyre, Argyll, and on the Isle of Arran will remain cut off overnight.

This number is down from 5,000 earlier today as around 400 engineers continue their efforts to restore supplies, it said.

The provider said it is the first time in the company's history that two of its metal pylons have come down. It said the last time a pylon was felled by severe weather was in 1987, in the north of Scotland.

An SSE spokesman said: "Instances of significant damage to the electricity network infrastructure have been among the worst seen for 30 years, with the weight of line icing pressurising the transmission lines around Crossaig where transmission towers were felled by the conditions.

"Transmission overhead lines staff have started working to make towers safe and carry out temporary repairs after finally gaining access to the location earlier today."

Snow and gales blasted the west coast on Friday, plunging 18,000 properties into darkness.

Arran suffered a complete blackout and mainland areas in Kintyre and Dumfries and Galloway were also badly affected.

Helicopters were used over the weekend to identify faults and inform engineers of their locations.

In Galloway, ScottishPower said it hopes to have power restored this evening to the last remaining 100 homes and businesses that were cut off over the weekend.

It said 300 engineers have been on the ground in Wigtownshire and Barrhill working to re-connect people, and the number of those without power has fallen from about 3,000 on Sunday morning.

Heavy snow and high winds have hampered efforts to restore supplies, as engineers were unable to get to damaged lines because of blocked roads.

A ScottishPower spokesman said: "We would again like to thank customers for the patience they have shown, and apologise for the inconvenience caused. Our engineers have encountered some of the most difficult conditions they have ever faced attempting to restore supplies."

Engineers from Scottish Hydro Electric Power Distribution (SHEPD) will continue work in Kintyre and Arran into the night and will resume their duties early tomorrow.

SSE said, in addition to the 400 engineers it has in the field, a further 100 people are working in supporting offices, with others on stand-by.

SHEPD has organised eight mobile hot food outlets in Argyll and Arran, while 18 large generators and 50 smaller sets have been installed in the areas.

"SHEPD is currently in the process of contacting affected customers by telephone and any customer who will be without power overnight will receive a call this evening," the SSE spokesman said.

As the snow begins to clear, vital routes are being reopened, including the A83 to Campbeltown, in Kintyre, where traffic was moving under police convoy today.

The Tangy Mill and Glenbarr loop roads are also open, and heavy machinery has been used to help clear the Clachan loop road and routes to Mull that were blocked.

Teams have been working to clear other roads blocked by snow and low-lying power cables, including the B8001 to Skipness, Barr Glen, Learside, Glenbreckerie, Lossit and Gobagrennan.

Another Scottish Government Resilience meeting has taken place to help co-ordinate the response, the sixth meeting since Friday afternoon.

Transport Minister Keith Brown said: "Across the affected parts of Scotland, emergency power engineers and road crews are working extremely hard to restore electricity and clear transport access as quickly as possible.

"The level of multi-agency co-operation and the support received from local communities and voluntary groups is to be highly commended.

"The Scottish Government will continue to do everything we can to support local responders and help co-ordinate the support and help they need until all services are restored."

Emergency supplies and medical help have been delivered to communities by the Royal Navy search and rescue helicopter HMS Gannet, and the RNLI has taken milk and other essentials over to Arran by lifeboat.

NHS Ayrshire & Arran said Arran War Memorial Hospital is operating on a back-up generator and has full power.

Brodick, Lamlash and Shiskine GP surgeries are open, and a doctor is providing community based care for patients in the Lochranza area.

A spokeswoman said: "Members of the public are asked to not contact the hospital directly. This is to allow the hospital staff to care for the increased number of patients."

ScottishPower said later that all of the affected properties in Galloway have been re-connected.