By Ingrid Melander

BRUSSELS, Sep 4 (Reuters) Last month's London bomb plot shows the need for European countries to work more closely to improve detection of explosives and dangerous substances, the European Commission said today.

It called on EU states to consider common EU certification and standards for equipment such as security arches, hand-held metal detectors and other devices used at airports and major gatherings such as sporting events.

Authorities from the bloc's 25 countries should also share best practice about how to search the Internet for sites which contain such things as bomb manuals, the EU executive said in a consultative report.

''Recent events in the UK have further underlined that detection devices must be continuously improved in order to reflect the ever changing threat posed by terrorists and criminals and to ensure that people are able to travel safely,'' EU Justice Commissioner Franco Frattini said in a statement.

British anti-terrorism detectives said on August 10 they had foiled a plan to use homemade liquid explosives to bring down several airlines on the way from Britain to the United States.

Airport screening is largely the same in mainland Europe as it was before August 10, except for U S- and Britain-bound flights.

But the scare has prompted discussion of what EU-wide action can be taken to make airports more secure. Frattini's spokesman said EU experts would discuss on Wednesday and Thursday possible changes to EU rules on taking liquids on board flights.

Liquid and cream gels may be banned from hand luggage on European flights, sources familiar with the discussions said. A Commission official said strengthening detection could help ensure hand-luggage was not banned altogether at some point.

Establishing common standards on detection tools such as metal detectors could also help the industry know what products to offer to EU airports, the official said.

''The market already offers a number of detection products.

However, very often it is difficult to identify what tools and products are the best or at least meet certain minimum requirements,'' the European Commission report said.

''An EU-wide system of certifying good quality tools and benchmarking them ... could address this deficit,'' it said.

The air transport industry, keen to prevent expensive delays and a drop-off in passenger traffic like the one after the September 11, 2001, attacks on the United States, insists any changes to regulations are proportionate to the actual risk.

The EU is already working on ways to make air travel safer by collecting more extensive passenger information and using biometric passports.

REUTERS AB HT2110