Big increases in online orders of pharmaceuticals, alcohol and department store products during the coronavirus pandemic have fuelled delays to parcel delivery times across Australia.

At the same time, Australia Post has warned of reductions in its air freight capacity as airlines have cut back their services, which means letters and parcels will take longer to arrive at their destination – particularly in regional and rural communities.

An Australia Post spokesperson said the organisation was currently seeing “a big increase in our parcel volumes, similar to what we experience during Christmas time and during online sales such as Black Friday and Boxing Day”.

Over the past four weeks, for example, the volume of pharmacy-related parcels – including vitamins, medicines and hygiene goods – is 236% higher than it was at the same time last year.

Parcels in the department store category have grown by 184% compared with the same period last year, with major retailers either closing their doors and pushing sales online, or seeing a general increase in people wanting to avoid in-store shopping.

There also has been a big increase in wine and liquor parcel volumes, which have gone up by 168% compared to the same period last year. This figure includes products bought from major liquor retailers but also small business owners such as cellar doors which have had to innovate and switch to online sales.

Australia Post said it had taken steps to protect its employees and customers, including introducing physical-distancing measures and moving to contactless delivery. Customers no longer have to sign for parcels.

But increased volumes and additional breaks for hand hygiene purposes have contributed to delays. Retailers have also had to take time to process a flood of orders from customers.

A Target spokesperson said the retailer had seen a significant increase in demand for its online services over the last few weeks, which had “impacted stock availability on some of our more popular lines and has also meant home deliveries may take a little longer than usual”.

Target reported rising demand for gym and fitness equipment, home office and stationary, homewares and comfort clothing.

Big W, too, has reported a growing volume of online orders and has reduced its weekday trading hours to give its staff more time to fulfil these orders.

While Australia Post’s parcel volumes are booming, other parts of the business have experienced declines as the health response to the Covid-19 outbreak ushers in major changes to the country’s economic and social life.

“Although our parcels to consumers are growing strong right now, our letters business, our international business and many of our other great services such as providing passports, have almost immediately shrunk,” the spokesperson said.

“Even though we are seeing a large number of letters through our business, we have witnessed our letter volumes fall over 45%, as has our international revenues and some of the other key services like passports, have halved.

“Around 97% of our letter volumes come from businesses, and as they close their doors, they send less.”

Australia Post announced on Tuesday that reductions in air freight capacity would result in delays in delivering letters and parcels.

It said delays would mean that priority mail services may be suspended. Delivery times for Perth and Brisbane may increase by up to five days; north Queensland by up to seven days, and Tasmania by three days.

Australia Post also warned that it may not be able to maintain next-day express post services into regional and rural communities. It said it was exploring all available transport alternatives and options while working with the federal government to minimise impacts for customers.

The health department has advised mail and cargo workers to follow similar hygiene procedures that apply across the community more generally, including washing their hands frequently with soap and water and staying more than 1.5 metres away from other people.

It says there is “not considered an increased risk to cargo and mail workers as on most dry surfaces, coronaviruses die within a few hours as secretions dry out”.

The department also points to advice from the World Health Organisation that it is safe to receive international letters or packages.

The union representing postal workers has urged delivery drivers who haven’t been provided with portable supply of hand sanitiser to avoid delivering an article to a home or business location if it would require touching any hard surface such as door handles, intercoms or lift buttons.