DAKAR (Reuters) - Togo must go the way of other West African nations and swiftly limit presidential terms to two if it wants to prevent protests escalating into a political crisis, the United Nations envoy to the region said on Saturday.

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Thousands of people have taken to the streets in the past three days to demand that President Faure Gnassingbe step aside, in the most serious challenge to his family’s 50-year ruling dynasty since the death of his father in 2005.

Police have responded with tear gas, although avoiding the bloodshed that has tarnished previous demonstrations, and internet and phone calls have been restricted.

There were no further reports of protests on Saturday, and they seemed to have died down, but the opposition said they would continue until Gnassingbe steps aside.

“It has become unavoidable for Togo to join the rest of West Africa in having term limitations,” U.N. Special Representative for West Africa and the Sahel Mohamed Ibn Chambas told Reuters in a telephone interview.

Since Gambia’s Yahya Jammeh was forced out after losing an election last December, all West African countries except Togo have accepted two-term limits on presidential office -- bucking a regressive trend across Africa to remove them and re-enable “presidents for life”.

“Our main perspective is to advise the Togolese to take those actions to prevent an escalation,” he added. “We are in a region where the security challenges are real and menacing and so we don’t want to see any deep political crisis.”

He said a move by Gnassingbe’s government this week to propose a draft bill to reform the constitution and reintroduce a two-term limit was welcome. The opposition has rejected it because it says it would enable him to stay in power until 2030.

“I suspect the devil is in the detail. We have to wait to see the formulation of the draft,” Chambas said.

An official in Gnassingbe’s cabinet did not immediately respond to a request for comment, but Chambas said he had received assurances during his meeting with the president on Friday that he had “heard the people”.

The president’s father Gnassingbe Eyadema seized power in a 1967 coup and ruled for 38 years before his death. He brought in a two-term limit in 1992, in response to protests, then scrapped it a decade later when he decided he wanted to run again.

When he died in 2005, the military installed his son instead of the national assembly head, as was constitutionally mandated, stoking protests in which at least 500 people were killed.

Faure Gnassingbe has since sought to remodel Togo as a shipping, banking and airline hub modeled on Dubai or Singapore, with some limited success in port upgrades, regional airline operator Asky and pan-African bank Ecobank.

Chambas urged the government to move swiftly with changes.

“My biggest fear for it to go to the national assembly and there be a total blockage. I hope there will be a clear time line...not a perception that this is a delaying tactic,” he said. “That will go a long way toward building confidence.”