Clues to the mystery of why Viking colonies in Greenland thrived and disappeared have been found in the DNA of medieval walrus bones housed in more than a dozen European museums.

On Greenland, they had elaborate stone churches with bronze bells and stained glass, a monastery, and their own bishop. Their colonies at one time supported more than 2000 people. And then they vanished.

The US Government says it will impose fresh sanctions on Russia after it determined that Moscow used a nerve agent against a former Russian agent and his daughter in the UK.

Sergei Skripal, a former colonel in Russia's GRU military intelligence service, and his 33-year-old daughter, Yulia, were found slumped unconscious on a bench in March after a liquid type of nerve agent was applied to his home's front door.

The national building regulator needed to be "publicly exposed" for wasting taxpayer money after it made an "outrageous" decision to take legal action against two union officials for having a cup of tea, the federal court has said.

Federal Court Justice Tony North said the Australian Building and Construction Commission (ABCC) had wasted money taking legal action against the Construction, Forestry, Maritime, Mining and Energy Union officials.

Opposition Leader Bill Shorten is tightening drought assistance pressure on Prime Minister Malcolm Turnbull by calling for the government’s $12,000 cash grants to farmers to be accelerated to September 1.

Mr Shorten also announced a $20 million scheme to fund outback councils to create jobs.

Mr Turnbull on Sunday announced the scheme to be paid to drought-ravaged farmers on top of their $16,000 annual Farm Household Allowance.

However, some farmers criticised the plan as “too little too late”.

Another case of melting bitumen, this time on the Bruce Highway, has destroyed the tyres of at least one heavy vehicle in central Queensland overnight.

It comes after a similar incident affected a road in the state's far north early last month. The road surface started lifting overnight.

Today, the Department of Transport and Main Roads (TMR) confirmed resealing work had failed on a 2.4-kilometre stretch of the Bruce Highway between Rockhampton and Mackay.

The speed limit on five inner-Brisbane roads could be dropped to 40km/h to ensure the safety of 4000 Brisbane State High School students and parents crossing the major roads every day.

The behaviour of motorists on Cordelia Street, Vulture Street, Merivale Street, Gladstone Road and Ernest Street in South Brisbane is currently being assessed by Brisbane City Council.

The council’s infrastructure chairman Amanda Cooper said the council had progressively been installing school zones on busy multi-lane roads where pedestrian safety concerns existed.

More women candidates than ever will contest US governorships and House seats in November's mid-term elections.

After Tuesday's primaries across four states, there are now 11 female nominees for governor and at least 185 for the House of Representatives.

The results were hailed as a continuing success story by activists for women in politics.

Three young soccer players who were trapped with other team members for almost three weeks in a cave in northern Thailand were granted Thai citizenship on Wednesday along with their 25-year-old coach.

All four had been stateless, and their lack of citizenship deprived them of some basic benefits and rights, including the ability to travel outside of Chiang Rai, the northern province where they live.

The area is home to ethnic minorities with roots in neighbouring Myanmar.