VARZAGHAN, Iran — As their caravan of private cars drove north along the Tehran-Tabriz highway, following the five trucks they had filled up with relief goods for the victims of the deadly double earthquake that struck northern Iran this month, a group of young Iranians — a mix of hipsters, off-road motor club members and children of affluent families — felt like rebels with a cause.

None of the people in the cars seemed to know exactly how it had begun, or to remember how they all met during the past sleepless days. They became friends while standing in long lines in the parking lot of a privately owned building, passing along boxes filled with blankets and toys.

Energized by anger over widespread accusations that Iran’s official relief organizations were not adequately helping survivors, they, and hundreds of others, spontaneously organized a 48-hour charity effort using text messages, Facebook and phone calls to gather money and goods.

But instead of handing over their collection to the Iranian Red Crescent Society — which is close to the government — as the authorities had asked in the state media, these youths were determined to transport it themselves to the most remote hill villages ravaged by the earthquakes, which struck a rural Turkish-speaking part of the country. More than 300 people were killed and thousands left homeless.