The Foreign Office is investigating reports that a Briton may have been among the victims of a massive explosion which ripped through a tourist cafe in Morocco.
Morocco's government spokesman says that terrorists were behind the attack in the tourist city.
A Moroccan government spokesman said he believed the blast had been a "criminal act" and was not accidental.
The French paper Le Figaro claimed that a British man and two French nationals were among those killed.
Briton Hugo Somersham-Jones, who lives near the square, told the BBC: "It sounded like a bomb. I went outside and saw smoke and got to the cafe and saw falling masonry. I came out to the main square and saw the first floor of the cafe in ruins.
"People had fire extinguishers, trying to put out the fire, and others were pulling people out from the building - it was pretty bad."
Moroccan government spokesman Khalid Naciri told France-24 television: "We worked for more than an hour, maybe less, on the hypothesis that this could eventually be accidental.
"But initial results of the investigation confirm that we are confronted with a true criminal act."
Foreigners were among 15 people killed and 20 wounded in the main Djemma el-Fna in Marrakech in what the Moroccan government described as a criminal act.
"We are aware of the report. The Foreign Office is looking into it," a Downing Street spokeswoman said.
"A consular team from the embassy has been despatched."
A Foreign Office spokesman said: "The FCO are aware of a large explosion in the Argana restaurant in Djemma el-Fna Square.
"There are reports of several deaths and injuries. Consular staff have been deployed and are urgently trying to establish whether any British nationals are involved."
Andy Birnie, of north London, who is on his honeymoon, witnessed the blast in the square which is well-known for its snake charmers, fire breathers and old town.
He said: "There was a huge bang, and lots of smoke went up, there was debris raining down from the sky. Hundreds of people were running in panic, some towards the cafe, some away from the square. The whole front of the cafe is blown away.
"It was lunchtime so the square was very busy. We had just walked into the square, but were shielded by some stalls."