Syrian refugees in Lebanon will lose their status as such if they return home for a visit, the interior ministry said Saturday.
At the same time, there are calls for deporting those who voted in an election in which Syrian President Bashar al-Assad is certain to win.
More than a million Syrians have fled their war-torn country for Lebanon in the past three years, according to the United Nations.
"Syrian displaced people who are registered with the UN High Commissioner for Refugees are requested to refrain from entering into Syria starting June 1, 2014, or be penalised by losing their status as refugees in Lebanon," said the ministry.
The statement, published by the National News Agency, said the measure is grounded "in a concern for security in Lebanon and the relationship between Syrian displaced and Lebanese nationals... and in a bid to prevent any friction between them."
The decision, which takes effect Sunday, comes two days after tens of thousands of Syrians flocked to their Beirut embassy to vote in the election.
Lebanon's March 14 coalition, which opposes Assad and its Lebanese allies, said those who voted "should be deported immediately... because their security in Syria is not under threat."
The refugee influx into Lebanon has burdened the tiny Mediterranean country's weak economy, with politicians on all sides calling for measures to limit the flow.
Lebanon has not signed the Convention on Refugees, and refers to Syrians forced out of their country by war as "displaced."
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Most Syrian refugees in Lebanon live in informal camps dotted around the country, mainly in border areas in the north and east.
The authorities say the actual number of Syrians in Lebanon is far higher than the nearly 1.1 million accounted for by UNHCR.
Lebanon has frequently complained it lacks the necessary resources to cope with them, and that the labour market is struggling to accommodate them.
Foreign Minister Gebran Bassil warned Thursday that the country would "collapse" if the influx continues to soar.
He also said Beirut was taking measured aimed at "putting an end to the Syrian migration wave to Lebanon."
Lebanon, dominated by Damascus for nearly 30 years until 2005, is still sharply divided into pro- and anti-Assad camps.
It has also seen a spillover of Syria's violence, killing scores in the past three years, mainly in battles and explosions.
On Saturday, the Lebanese army said an explosive device planted inside a vehicle detonated during the night in the border town of Arsal, wounding two people.
A local official in Arsal told AFP the vehicle had a Syrian registration plate, and that "a personal dispute" had been behind the attack.
Arsal is home to more than 100,000 Syrian refugees.