Chief Executive John Lee has called on senior officials of his administration not to underestimate the impact of Super Typhoon Ragasa as there are still uncertainties about the storm.

The city's leader also said on Monday he had ordered officials to activate the Emergency Monitoring and Support Centre in advance and met Chief Secretary Eric Chan and Secretary for Security Chris Tang at the centre to discuss readiness plans.

"The path and intensity of Ragasa remain uncertain. The government will continue to monitor the latest developments and adjust its arrangements," Lee wrote on social media.

"I have asked all bureau heads and department chiefs not to underestimate the power of the typhoon and that they plan well ahead and be fully prepared."

He also urged the public to stay vigilant and pay attention to latest developments on the storm front.