Increased fighting in recent weeks around Aleppo has swelled the number of Syrian refugees stranded at the border with Jordan to more than 64,000, Jordanian border guards said on Thursday.
The kingdom said in April that about 50,000 Syrians were stuck in no-man's land, a three-fold increase since January when it imposed tough security checks at the Hadalat and Rokbane crossings.
Border guards said Thursday that there were now in excess of 64,000 Syrians along the frontier, including more than 5,000 who arrived in a 24-hour period last week.
"The number of refugees has hit 59,000 at Rokbane and it's rising," the head of Jordan's border guards, General Saber Al-Mahayra, told reporters on Thursday.
Another officer told AFP that 5,000 others were massed at Hadalat, about 70 kilometres (40 miles) further west.
Mahayra said nearly 5,500 had arrived at Rokbane since last week, an influx he partly attributed to increased fighting around Syria's second city Aleppo, where more than 280 civilians have died in recent weeks.
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Jordan, which is already home to 630,000 registered Syrian refugees, has insisted it must screen newcomers to ensure they are genuine refugees and not jihadists seeking to infiltrate the country.
The kingdom is now allowing in only a few dozen refugees each day after screening.
According to Mahayra, around 2,000 Syrians currently camping near the border are suspected by Jordanian authorities of involvement with the Islamic State group.
Weapons have already been seized from some would-be refugees along the border, he added.
After Syria's conflict erupted in 2011, Jordan initially kept open 45 crossing points along its 378 kilometre (235 mile) frontier.
But after a mass influx into the kingdom -- Amman says the true number of Syrians in Jordan is closer to 1.4 million -- there are now just five crossing points open, and three of those are reserved for the wounded.
Syria's conflict began with anti-government protests but fighting quickly escalated into a multi-faceted war that has killed more than 270,000 people and forced millions from their homes.