A rule that airline passengers can only take carry-on bags within a standard weight and size should be enforced by airlines from May 1, the country's civil aviation authority has said, a Beijing-based newspaper reported.

The luggage should be no larger than 20x40x55 centimeters in size and no heavier than five kilograms, China Youth Daily said, citing the Civil Aviation Administration of China (CAAC).

If the luggage is larger or heavier than the standards, passengers must check-in the bags, the report added.

The administration reminded passengers to be aware of the policy to avoid any unnecessary flight delays, the report said. Economy- and business-class passengers are allowed one carry-on bag while first-class ticket holders can take two bags aboard a plane.

The administration initially launched the rule in 2000. It reiterated it 105 days ahead of the Beijing Olympics.

Security at airports and on planes has been beefed up after two suspected terrorists were caught on a plane from Urumqi in the Xinjiang Uygur Autonomous Region that was destined for Beijing on March 7.

On April 7, the administration banned passengers from taking lighters or matches aboard planes, which followed a ban on liquids, previous reports said.

The administration ruled on March 27 that airport security staff are required to check passengers' shoes for concealed knives, explosive materials or other forbidden items.

Meanwhile, airlines in cities such as Shanghai, Wuhan, Guilin, Jinan and Zhengzhou banned passengers from taking more than two lithium batteries onboard for each electronic item as the batteries are considered flammable, previous reports said.