Weary travellers will begin arriving home from Thailand on Tuesday on a series of evacuation flights ferrying Australians caught up in a siege of Bangkok’s main airports.

Three hundred passengers, mostly Australians and British Airways ticket-holders, will board a Qantas flight from Phuket to Singapore late on Monday, where they will be able to connect to flights home.

They are among thousands of travellers who have been caught up in anti-government protests in Bangkok, where the People’s Alliance for Democracy (PAD) have blockaded the city’s two main airports.

And there are fears the political strife will escalate into clashes between the PAD and pro-government supporters.

The Department of Foreign Affairs and Trade (DFAT) on Monday upgraded its travel advice for Bangkok, urging Australians to think twice before travelling to the Thai capital.

“You should avoid unnecessary travel to the area around Government House and other demonstration sites,” it advised on its smarttraveller website.

“Several attacks, including with hand grenades and explosive devices resulting in some fatalities and a number of injuries have occurred. Further violence cannot be ruled out.”

Qantas will run another relief flight out of Phuket late on Tuesday, part of an effort by airlines to boost services from alternative airports to clear the thousands of passengers stuck in Bangkok.

To get to Phuket, passengers will have to endure a 14-hour bus trip from Bangkok, before boarding the 90-minute flight from Thailand to Singapore.

They then face at least another eight hours on a plane to get to eastern Australian capitals.

Qantas chief executive Alan Joyce says the airline will consider adding more flights out of Phuket, if required.

And budget airline Jetstar is rescheduling flights to Melbourne – which normally leave from Bangkok – out of Phuket.

Officials are examining if it’s possible to get Australians out on flights from Utapao military base, about 150km from Bangkok.

Travellers who have managed to get on Thai Airways flights from Utapao expressed surprise that some have been half empty.

Foreign minister Stephen Smith, who is in Europe, said the main problem had been “logistical difficulties” in getting access to the airports.

“We have been becoming very frustrated with the Thai authorities, particularly Thai airline authorities and tourism authorities,” he said.

Australian authorities aren’t hiding their frustrations at the political chaos in Bangkok.

The violence is expected to cause the delay of an Association of South-East Asian Nations (ASEAN) summit in Chiang Mai, which Prime Minister Kevin Rudd is due to attend, later this month.

Trade minister Simon Crean urged the warring political factions to resolve their differences, reminding them of the harm the protests were doing their nation.

“These demonstrations and protests are causing enormous damage to the economy of Thailand, it relies very heavily on the tourism market, but it is also a significant trading facility within the region,” he told parliament.

“Our very strong urging, through the frustration that we’re experiencing, is to the parties involved in this to resolve their differences and get the country back to normal.”