An attack on a crowded night club in the Mexican city of Guadalajara has left six people dead, police say.
Unidentified gunmen sprayed the city centre bar with bullets and threw a hand grenade before driving away.
Police said the attackers were customers who returned to exact revenge after a late-night dispute with other drinkers.
Guadalajara - Mexico's second city - has seen a sharp rise in drug-related violence in recent months.
The Butter Club, in a wealthy neighbourhood near the centre of Guadalajara, was packed with customers when the attack happened in the early hours of Saturday morning.
Among the dead are a Colombian and a Venezuelan citizen.
At least 20 people were wounded in the shooting and grenade explosion, and some are reported to be in a serious condition.
Guadalajara, in the western state of Jalisco, had for a long time been spared the worst of the drug-related violence afflicting some other states.
But killings have escalated over the past year, as rival cartels fight for supremacy.
Earlier this month gunmen with automatic weapons blocked main roads in the city with burning vehicles in a replica of scenes that have become frequent in some cities in northern Mexico.
On 3 February the US consulate in Guadalajara warned of a "marked escalation of criminal activity" and banned US officials from travelling on the main road to the airport after dark.
The increase in violence comes as Guadalajara prepares to host the Pan American Games in October.