Germany is imposing an entry ban on 18 Saudi citizens who are believed to be connected to the murder of Saudi journalist Jamal Khashoggi, Foreign Minister Heiko Maas said on Monday on the sidelines of a European Union meeting in Brussels.

Khashoggi, a contributing Washington Post columnist and a sharp critic of Saudi Crown Prince Mohammed bin Salman, was killed on October 2 in the Saudi consulate in Istanbul.

Saudi Arabia has come under pressure from the international community to provide more information on the incident.

The Foreign Ministry in Berlin last week called on Saudi Arabia to conduct a seamless and transparent investigation after Riyadh announced it had charged 11 people in Khashoggi's case.

Riyadh acknowledged the death of the columnist after he went to the consulate to collect papers needed for his marriage to a Turkish woman and failed to emerge.

Saudi prosecutors allege that a team of specialist assassins was sent to Istanbul by top-level Saudi government members to carry out the murder.

They have since called for the death penalty for five of those alleged to have been involved, out of a total of 11 charged.

Repeated press reports have linked Mohammed to the killing.

US media have based their reports on CIA documents made available to them alleging that Mohammed himself had ordered Khashoggi lured to the consulate for elimination.

But on Saturday, the State Department in Washington said no final conclusion about responsibility for the killing had been made, saying there were a number of unanswered questions.

Mohammed is reported to not be on the German list of 18 banned Saudis.