Mexico's former top anti-drugs chief has been charged with allegedly passing on information to one of the nation's most powerful drug cartels.

Noe Ramirez is accused of accepting bribes of up to $500,000 from the Sinaloa cartel to warn the group's leaders of police operations against them, the Mexican attorney general's office said on Sunday.

Ramirez resigned last July from the country's Siedo organised crime unit and was arrested in November following a government probe.

His arrest was the most high profile so far in the probe, aimed at uncovering police and government officials working for drug smugglers.

The news comes as violence continued in Mexico after at least 11 people, including six children, were killed in three drive-by shootings in Mexico's southeastern
Tabasco state, local authorities said on Sunday.

The dead were mostly relatives of a Mexican state police officer, officials said.

Drugs violence

Ramirez was appointed as Mexico's top anti-drug prosecutor by Felipe Calderon, Mexico's president, in 2006.

Two other anti-drug officers were imprisoned in 2008 for accepting bribes of up to $500,000 from the Beltran Leyva gang, which had recently split from Sinaloa cartel.

Calderon's two-year-old crackdown on drug cartels has sparked brutal violence as cartels battle for turf and power, with around 6,000 people dying in the fighting last year, many of them civilians.