Cyprus expressed optimism on Wednesday that it could contain the island's worst forest fire in years after additional firefighting aircraft arrived from France and Italy.

The government meanwhile declared three days of mourning from Wednesday for two firefighters killed as the blaze raged in the Solea valley in the northern foothills of the Troodos mountains.

President Nicos Anastasiades was set to attend their funerals and has cancelled all his official activities until the end of the week.

Three French and one Italian aircraft joined two British, four Greek and six Israeli aircraft that were already helping to tackle the second massive wildfire to hit the Mediterranean holiday island in less than a week.

Cyprus government spokesman Nicos Christodoulides said that with so many planes in the air he was "optimistic" the fire would be brought under control soon.

"Today we hope that with the help from so many countries in the air we can succeed in controlling the fire," he told public radio.

Christodoulides said Russia too had offered to send firefighting planes but he said they might not be needed.

The blaze, which has raged since Sunday, has destroyed at least 15 square kilometres (six square miles) of farmland and forestry.

Efforts to control it have been hampered by the tinder-dry conditions as the island swelters under temperatures topping 40 degrees Celsius (104 Fahrenheit).

Funerals for the firefighters were to take place separately on Wednesday and Thursday, authorities said.

They died in hospital on Monday from injuries suffered when the truck they were in plunged 40 metres (130 feet) down a cliff.

Flags would be flown at half-mast on government buildings during the three-day mourning period, authorities said.