MEXICO CITY — In a major strike against one of Mexico’s largest drug-trafficking organizations, the Mexican Navy said Thursday that it had detained one of the most sought-after drug kingpins in Mexico and the United States, the top leader of the Gulf Cartel.

In an early morning news conference in Mexico City, the man, Jorge Eduardo Costilla Sánchez, who faces an array of charges in both countries, was marched before reporters by masked marine guards. A stocky man handcuffed in front and dressed in a checkered shirt and jeans and wearing a bulletproof vest, he looked sternly at the gathering, standing before a table covered with rifle parts, jewelry, a couple of gold-plated handguns and other goods seized during his arrest Wednesday evening.

José Luis Vergara, a marine spokesman reading a statement, said Mr. Costilla, 41, known as El Coss, was detained without any resistance by about 30 marines around 6 p.m. in Tampico in northeastern Tamaulipas State. Several other people detained with him were also shown to reporters, some of them with facial cuts and bruises.