A BBC correspondent who visited the northern Syrian town of Saraqeb says he heard witness accounts and watched video recordings that lend credence to reports that a chemical weapons attack took place there last month.

Ian Pannell also visited a local hospital where doctors reportedly said eight people had been admitted with breathing problems after the town was attacked by government artillery on April 29. The doctors said some of the injured were vomiting, and that a woman named Maryam Khatib eventually died from her injuries.

The BBC report cited videos purporting to show a helicopter passing over the town and dropping at least two smoking objects that local residents said contained poisonous gas. The BBC said it could not verify the authenticity of the videos but that they were being analyzed abroad.

Both sides in the Syrian civil war have accused the other of using chemical weapons.

Last month, the British-based Syrian Observatory for Human Rights said doctors treating several people wounded in an air raid in Aleppo, near Saraqeb, showed signs of inhaling toxic gas, such as severe vomiting and irritation to the nose and eyes.

Officials with Syrian President Bashar al-Assad's regime have asked the United Nations to investigate an alleged chemical weapons attack by opposition fighters in March on the village of Khan al-Assal, outside of Aleppo, that killed 31 people. The opposition blames regime forces.

UN investigators denied full access to investigate

The Assad regime has not allowed a team of experts into the country because it wants the investigation limited to the single Khan al-Assal incident, while UN Secretary General Ban Ki-moon has asked for "immediate and unfettered access" for an expanded investigation.

Britain and France want the UN to investigate allegations of chemical weapons use in Khan al-Assal and another village, Ataybah, on March 19, as well as the central city of Homs on Dec. 23.

U.S. President Barack Obama has said the use of chemical weapons in the Syrian civil war represented a "red line" for his administration and could prompt a change in U.S. policy toward the conflict, which has resulted in at least 70,000 deaths, according to the latest UN estimate.

Obama said the U.S. government is still investigating the allegations.

On Thursday, he met with Turkish Prime Minister Recep Tayyip Erdogan in Washington, where they discussed a range of issues including trade, security and Syria.

Under a pair of umbrellas outside a drizzly White House, the two leaders offered no hints about new actions either country would take, but pledged to keep upping the pressure on Assad to leave.

Obama praised the Turkish people for the "extraordinary generosity" they have shown Syrians who fled to Turkey and said the U.S. will continue to assist with humanitarian relief in the region.

The U.S. president said he and Erdogan "both agree that Assad needs to go. He needs to transfer power to a transitional body."

Erdogan said the U.S. and Turkey also agreed that preventing Syria from "becoming an area for terrorist organizations" was a priority.

"We also agreed that chemical weapons should not be used, and all minorities and their rights should be secured," the Turkish prime minister said, though he did not offer specifics about how that  might be achieved.

With files from The Associated Press