BRUSSELS: The European Union Monday imposed sanctions against 16 more high-ranking military Syrian officials and scientists over chemical weapons attacks on civilians, a statement said.

The move by the bloc's foreign ministers brings to 255 people now facing a travel ban and an assets freeze over President Bashar Assad's violent crackdown on civilians during a five-year civil war.

"The EU added these 16 persons for their role in the development and use of chemical weapons against the civilian population," an EU statement said.

The EU will release the names of those hit by the sanctions on Tuesday, it said.

The U.N.'s chemical watchdog, the OPCW, last month concluded that sarin was used as a chemical weapon in the April 4 attack in the Syrian town of Khan Sheikhun that killed at least 87 people including children.

The sanctions decision "shows the resolve of the UK and the rest of our friends in Europe in dealing with those who are responsible for chemical weapons attacks," British Foreign Secretary Boris Johnson told reporters just before the decision was announced.

Syria is already subject to an oil embargo, restrictions on certain investments, a freeze of the assets of the Syrian central bank held in the EU, as well as export restrictions.

It also is under sanctoins on equipment and technology that might be used for internal repression as well as on equipment and technology for the monitoring or interception of internet or telephone communications.