BEIRUT (AP) Lebanon began imposing unprecedented restrictions Monday on the entry of Syrians, as the tiny country with a fragile sectarian balance struggles to cope with well over a million refugees feeling the civil war next door.

Syria's war has displaced nearly half its pre-war population, sending over three million people across borders, mainly to Lebanon, Turkey, Jordan and Iraq. Western countries have only accepted small numbers of refugees, and hundreds of people have drowned attempting to cross the Mediterranean Sea on rickety smuggler ships.

Lebanese officials say they simply can't absorb any more. They estimate there are about 1.5 million Syrians in Lebanon, about one-quarter of the total population. Some 1.1 million are registered with the U.N.'s refugee agency.

"We have enough. There's no capacity anymore to host more displaced," Interior Minister Nohad Machnouk said in a press conference carried on local television.

Lebanon has been hosting hundreds of thousands of Palestinian refugees since Israel's creation in 1948, and their presence was a central factor in the 1975-1990 civil war. The war in Syria has already escalated tensions between Lebanon's Shiites and Sunnis, and many fear the influx of the mainly Sunni refugees could again aggravate the tiny country's delicate multi-sectarian balance.

The changes that went into effect Monday establish new categories of entry visas for Syrians including tourism, business, education and medical care and sharply limit the period of time they may stay in Lebanon. But the restrictions, which were announced last week on Lebanon's General Security Directorate website, seemingly make no provisions for asylum seekers.

For decades, Syrians were freely given six-month visas and many simply crossed the porous border without any paperwork at all.

But when Syria's 2011 uprising collapsed into a civil war, hundreds of thousands poured into Lebanon, overwhelming the country's water and power supplies, pushing up rents and depressing the economy in rural areas, where they compete with impoverished Lebanese for scarce jobs.

Tent cities have sprouted in rural areas with many of the refugees confined to flimsy shelters now battered by winter rains and snow. Public opinion has sharply turned against the Syrians, who many see as threatening the sovereignty of Lebanon long-dominated by its larger neighbor.

Lebanese border officials began informally restricting the entry of Syrians in October, which has already caused a 50 percent drop in people seeking to register with the U.N.'s refugee agency, the UNHCR. Local television showed a once crowded and chaotic border crossing nearly empty on Monday.

"We are looking at these new procedures with some interest, because those procedures don't make mention of the agreement of the government to continue to allow the most vulnerable cases to come through," said UNHCR's regional spokesman Ron Redmond.

He said even after informal limitations were introduced last year, the Lebanese government was still allowing in Syrians they deemed "urgent cases" single women fleeing with their children, those needing urgent medical care and children separated from their families.

"We didn't see any reference to that in these new regulations," Redmond said. "We want to get some kind of official documentation and description of how that's going to work."

A Lebanese security official, who spoke on condition of anonymity because he wasn't authorized to speak to the press, said urgent humanitarian cases could still enter, and that Syrians could make use of a medical care category and a 48-hour visa that would allow them to apply for asylum at foreign embassies.

On Saturday, the Syrian Ambassador Ali Abdel-Karim called on Lebanon to "coordinate" its new measures with Damascus.

Amid wide approval in Lebanon for the restrictions, a prominent newspaper editorial urged Lebanese to act humanely.

"We know that the burden of the Syrian crisis, open to an abyss, is greater than what Lebanon can bear," Talal Salman wrote in As-Safir. "But it is able, certainly, to carry some of its weight." The refugees, he added, "left with their faces etched in worry, to the closest asylum they know."