Muslim leaders have called for mass protests at Friday’s noon prayers.
The shrine is revered by both Muslims and Jews.
Muslim leaders say Israel is trying to expand its control there by installing the security devices.
Gates were fitted with metal detectors after Palestinian gunmen launched an attack from there last week, killing two Israeli policemen.
Muslim leaders have called on worshippers to pray in the streets near the shrine rather than walk through metal detectors.
Over the course of the week, growing numbers of Palestinian worshippers have participated in street prayers, particularly in the evenings.
Following the prayers, small numbers of Palestinian protesters have clashed with police.
On Thursday evening, police fired rubber bullets, tear gas and stun grenades to disperse protesters who, according to police, threw rocks and bottles.
Paramedics from the Red Crescent said 37 people were injured by rubber bullets, three of them seriously.
Police spokesman Micky Rosenfeld said on Friday that reinforcements were being deployed in and around Jerusalem's Old City, where the walled shrine is located.
"Police and border police units mobilised in all areas and neighbourhoods,” he said.
Friday is the highlight of the Muslim religious week, and tens of thousands of worshippers typically perform prayers at the shrine, known to Muslims as the Noble Sanctuary and to Jews as the Temple Mount.
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