U.S. President Barack Obama has expressed his support to Mexican President Felipe Calderon for Mexico's efforts to control drug cartels.

In a Saturday telephone conversation, Mr. Obama also expressed his condolences for the deaths of two Mexican security officials and a journalist killed Friday in a gunbattle that also resulted in the death of Ezequiel Cardenas Guillen, a leader of the country's powerful Gulf drug cartel.

The battle took place in the border city of Matamoros, across from the U.S. city of Brownsville, Texas.

Cardenas was one of Mexico's most wanted drug gang leaders.

Mexican authorities had offered a $2 million reward for information leading to his arrest and capture, while the U.S. had a $5 million bounty on Cardenas.

He was considered a key smuggler of marijuana and cocaine into the U.S.

Cardenas took over the leadership role in the Gulf cartel after the 2003 capture of his brother Osiel Cardenas Guillen, a former leader of the drug gang, who was later extradited to the United States.  

Mexican military forces have been engaged in a brutal struggle against the country's violent drug cartels.  Nearly 30,000 people have been killed in Mexico's drug war since President Felipe Calderon took office in late 2006 and began cracking down on the cartels.