Tennis players have been warned about security ahead of the start of the Mexican Open in the troubled Pacific resort of Acapulco.
The professional men's tennis association, the ATP, cautioned against travelling outside hotels.
Players were advised to leave the city immediately after being eliminated from the tournament.
Mexico's government has assured the ATP that appropriate security measures have been put in place.
Several arrests have been made following a recent spate of drug-related violence in the city.
A weekend of attacks on taxis in the city left 12 drivers or passengers dead, the Associated Press news agency quotes local police as saying.
Dozens of cars have also been burned in recent days but the motives were not clear, AP reported.
In January, the bodies of 15 headless men were found outside a shopping centre in the resort.
'A bit scared'
Among the players attending the six-day tournament, which opens on Monday, are the defending men's champion, David Ferrer of Spain, who said he had no fears about being there.
But David Nalbandian of Argentina said on Saturday he was thinking about withdrawing, adding that he also had a groin injury.
"It's a great and enjoyable tournament to play," he said.
"But for right now it's a little more difficult because of the security situation. We [players] are a bit scared about this and we're trying to decide what to do."
More than 34,000 people have been killed in drug-related violence in Mexico since late 2006.