TRIPOLI, Lebanon — Syria has tightened control of its borders with Lebanon and Turkey in recent days, laying fresh fields of land mines and sweeping through areas critical to rebel smuggling operations in a development that raises questions about how aid, lethal or non-lethal, would reach the armed opponents of President Bashar Assad.

The Syrian efforts have been aided, anti-Assad activists say, by the militaries of both Lebanon and Turkey, which have recently taken steps to obstruct actions of both the rebel Free Syrian Army and smugglers operating from their territory.

"We wish the Turks would be softer in allowing the Free Army to operate," said a Syrian activist in Turkey who uses the nom de guerre "Godfather" and helps provide communications and medical aid to activists inside Syria.

"Godfather" said the Turkish military was pushing FSA groups inside Turkey further and further from what are often ambiguously marked areas along the mountainous border with Syria. He also said that Syria 10 days ago had placed new land mines along its side of the border.

At a meeting of countries working for Assad's ouster in Istanbul, U.S. Secretary of State Hillary Clinton on Sunday said the United States was supplying logistical support to the rebels, including communications equipment and would nearly double economic aid to the opposition by another $12 million. Representatives of Qatar and Saudi Arabia said their countries would begin paying salaries to FSA fighters.

But "Godfather" suggested that such aid had not been widely distributed, though some supplies were still getting through because of the ruggedness and length of the border with Turkey.

Along the border with Lebanon, opposition activists report that the Syrian military has stepped up its presence in recent weeks as well.

"They are putting more snipers on the border, they shoot at anything that moves," said Abu Ammar, who is part of a group that transports wounded Syrians to Lebanon for treatment. For many, treatment at government hospitals, where they are in danger of arrest and imprisonment, is no longer an option.

Abu Ammar, who also helps refugees to escape Syria, said any increase of aid would be welcome.

"The refugees need camps, they need blankets, they need medical care," Abu Ammar said. "The foundation is running out of money to pay for surgeries."

Smuggling efforts along the Syria-Lebanon border also were seriously hurt last week when the Syrian military, apparently with the assistance of Lebanese intelligence, arrested two Syrian smugglers who had been instrumental in transporting wounded Syrians to Lebanon for treatment along routes that are also used to smuggle people and goods into Syria. One of the smugglers had been a key contact for journalists seeking to cover the violence inside Syria.

In the wake of the arrest of the Syrian smugglers, the Syrian military also raided the town of Qaa, on the Lebanese side of the border, which was a jumping off point for the smuggling of both non-lethal and lethal aid to the rebels, including the few weapons the FSA seems to be able to smuggle into the country. Journalists who have seen the arms shipments describe them as a relatively small number of assault rifles and rocket-propelled grenades.

Another key Lebanese exit and entry point for goods and people moving clandestinely across the border, Wadi Khalid, has been largely cut off by the Lebanese military, activists said. The Syrian army has shelled the area and conducted at least one raid there in December.