Four people have been killed in three separate motor vehicle crashes in Tasmania in less than 24 hours.

A married couple died when the motorcycle they were riding crashed into a hay bale on Lilydale Road, north-east of Launceston, about 3:00pm on Sunday.

Police said the hay bale fell off a truck passing in the other direction, and was still moving at the time of the crash.

Anyone who saw a white Western Star truck and trailer carrying large round hale bales between Westbury and Lilydale on Sunday have been urged to contact police.

Another motorcyclist was killed when he crashed at Bothwell in Tasmania's Central Highlands about 11:00pm on Saturday.

Road marks where a motorcyclist was killed when he crashed at Bothwell in Tasmania's Central Highlands ( ABC News )

The 57-year-old man from Molesworth was pronounced dead at the scene of the crash on Hollow Tree Road.

On Saturday night, Leigh John Williams, 26, of North Road, King Island was critically injured when the ute he was driving crashed on King Island about 10:00pm.

He was rushed to the King Island District Hospital but died early on Sunday.

The crash happened at the corner of Manana and East Wickham Roads at Yambacooma.

Emergency services also attended a head-on crash between two vehicles on the Midland Highway north of Turnbridge.

One person was seriously injured and was flown to the Royal Hobart Hospital.

Paramedics treated five others for injuries.