* Asia companies, govts report minor disruptions from cyberattack

* Cybersecurity professionals warn worse impact may yet be felt

* Businesses using older systems more vulnerable to attack

* Cyberattack has hit 200,000 victims in at least 150 countries

By Jeremy Wagstaff and Dustin Volz

SINGAPORE/WASHINGTON, May 15 (Reuters) - Asian governments and businesses reported some disruptions from the WannaCry ransomware worm on Monday but cybersecurity experts warned of a wider impact as more employees turned on their computers and checked e-mails.

The ransomware that has locked up more than 200,000 computers in more than 150 countries has been mainly spread by e-mail, hitting factories, hospitals, shops and schools worldwide.

"Most of the attacks are arriving via e-mail, so there are many 'landmines' waiting in people's in-boxes," said Michael Gazeley, managing director of Network Box, a Hong Kong-based cybersecurity company.

In China, the world's second-largest economy, energy giant PetroChina said payment systems at some of its petrol stations were hit, although it had been able to restore most of the systems. Several Chinese government bodies, including police and traffic authorities, reported they had been impacted by the hack, according to posts on official microblogs.

The official China Daily newspaper, citing Chinese tech firm Qihoo 360, said that at least 200,000 computers had been affected in China, with schools and colleges particularly hard-hit.

A spokesman for the Hong Kong Exchanges and Clearing, one of the region's biggest bourses, said all systems were so far working normally. "We remain highly vigilant," he said.

Companies have warned users and staff not to click on attachments or links. One school in South Korea barred its pupils from using the internet. Taiwan's government appeared to have escaped major infection, possibly because regulations there require all departments to install software updates as soon as they are available.

South Korea's presidential Blue House office said nine cases of ransomware were found in the country, but did not provide details on where the cyber attacks were discovered.

In Australia, Dan Tehan, the government minister responsible for cybersecurity, said just three businesses had been hit by the bug, despite worries of widespread infection. There were no reported cases in New Zealand.

BRIEF RESPITE

Cyber security experts said the spread of the ransomware had slowed since its appearance on Friday but that the respite might only be brief.

For one thing, the attackers or copycat attackers may have developed new versions of the worm, although a British-based security researcher who thwarted an earlier version of the worm told Reuters most of these reports had been proven false.