CANBERRA (REUTERS) - Australian Prime Minister Scott Morrison, facing criticism over plans to evacuate citizens and some Afghans from Kabul, said adverse weather expected in the coming days threatens to delay rescue flights from Afghanistan.

Australia said earlier this week it would send 250 military personnel to Kabul to evacuate its citizens and an unspecified number of Afghans who had been given visas after working for Australia during the 20-year war.

Australia has evacuated 26 people on one flight from Afghanistan, and Morrison said a further 76 were transported out of Kabul late on Thursday (Aug 19) on a British plane. Australia intends to fly evacuation flights in and out of Afghanistan regularly over the next week, Morrison said, but warned plans could be threatened by looming bad weather.

"The weather is closing in and that's going to present some challenges over the next few days," Morrison told reporters in Canberra, without providing details. His office could not elaborate and weather forecasts suggest mostly sunny conditions with a small chance of some rain.

Morrison has been mounting pressure to expedite the rescue of Australians and Afghans who worked for the country during its two-decade long involvement in Afghanistan. However, he has warned Australia was unlikely to be able to help all of those Afghans who had provided assistance, offering 3,000 visas to fleeing Afghans from Australia's existing humanitarian visa programme of 13,750 a year.

Britain by comparison has promised to take 20,000 people from Afghanistan over the next five years.

Both countries were part of a Nato-led international force that battled the Taleban and trained Afghan security forces in the years after the militants were ousted in 2001. More than 39,000 Australian military personnel served in Afghanistan and 41 of them were killed there.