Killing of Druze politician Saleh Aridi jeopardises national reconciliation efforts.
“I call on all the major political parties to take down their banners to set an example for others,” al-Ariss said.
Removing the posters would reduce tension in the country, he said.
Tension over banners
Beirut’s streets and buildings are plastered with posters, party flags and portraits of political and military leaders, including Hariri and Berri.
The banners are highly symbolic of the simmering divisions between communities in the Lebanese capital.
While posters of Hariri predominate in western Beirut, flags of opposition parties Hezbollah and Amal fly in the south of the city.
Arguments over the placement of political posters have often turned violent.
Last week, two people were killed in a dispute over the hanging of a banner in northern Lebanon.
The March 14 majority, led by Hariri’s Future Trend movement, is in talks with the opposition, led by Hezbollah, ahead of a national dialogue which will precede parliamentary elections due next year.