The Security Bureau on Saturday called on people intending to travel to Iran or Israel to change their plans and avoid non-essential trips to the two countries.
A "red" Outbound Travel Alert for the two countries flagged up a "significant threat" to safety.
The bureau noted that tensions have been escalating in the Middle East since late February.
"Those already there should monitor the situation, attend to personal safety and avoid protests and large gatherings of people," it said.
SAR residents requiring assistance in either of the two countries should call or message the Immigration Department's round-the-clock hotline on (852) 1868, submit an assistance request form online, or contact the Chinese embassy in Israel on (972) 3-5459520, or the embassy in Iran on (98) 912-2176035.
Edited by Thomas McAlinden
