A traffic sign that reads "no entry" is seen on a road on Wednesday, where a deadly car accident earlier this week killed nine people and injured seven others. (Yonhap)

The Seoul city government said Thursday it will reinforce traffic signs and road markings on one-way roads as part of safety measures following a deadly car crash that left nine people dead earlier this week.

"Although a no-entry traffic sign and a road marking are put up (at the accident site), we plan to reinforce them and install more to make them more noticeable to drivers throughout the day and night," a city official said.

On Monday night, a sedan driven by a 68-year-old darted in the wrong direction for some 200 meters on a one-way road near Seoul City Hall before crashing into sidewalk guardrails, striking pedestrians and ramming into two other cars.

The crash left nine people dead, most of them office workers nearby, and seven others injured, while the driver has also been admitted to a hospital for broken ribs.

A traffic sign that reads "no entry (one-way road)" is put up over the road facing the exit of the Westin Josun hotel from where the car left, but the vehicle still entered the road.

Some also point out that the traffic sign may be difficult to spot at nighttime, and the road sign marked at the entry of the hotel could cause confusion.

Seoul Mayor Oh Se-hoon ordered a comprehensive survey on all one-way roads in the city to prevent such safety hazards, and plans to cooperate with the police in case improvements are needed in the signal system of one-way streets. (Yonhap)