The deaths happened at about 9pm on Wednesday in a beach area called New Kru Town in the country's capital, Monrovia.

A pregnant woman was reportedly among those killed.

"The doctors said 29 persons died and some are on the critical list," deputy information minister Jalawah Tonpo told state radio.

He called it a "sad day for the country".

A witness said the stampede happened when armed men rushed the crowd in a robbery attempt.

"We saw a group of men with cutlasses and other weapons coming toward the crowd," Exodus Morias said.

"While running, some people dropped and others fell on the ground and walked over them."

Hundreds had been at the event and police spokesman Moses Carter said one person had been arrested.

Rev Abraham Kromah, who was putting on the event and has a church in the city, was also questioned.

The victims' bodies were taken to a morgue at the nearby Redemption Hospital.

President George Weah declared three days of national mourning and visited some of the survivors at the hospital on Thursday.

His office said the Liberian Red Cross and Disaster Management Agency had been called in to help.

Street gangs - known as Zogos - have become an increasing problem in Monrovia and other cities in recent years, according to residents.

They usually carry machetes and other small weapons.