MADRID — Demonstrators in Morocco today slapped a commercial blockade on a Spanish enclave, allowing in only some trucks in a dispute over alleged police violence and racism against Moroccans entering the city.

The protest came a day after the kings of the two traditional allies spoke by telephone to try to calm tempers in a conflict that began three weeks ago.

Police said that at dawn protesters started preventing all trucks from entering Melilla. But in midafternoon 11 trucks carrying fruit and vegetables — Melilla depends on Morocco for fresh produce — were allowed over the border, according to Gabriel Escobar, the Interior Ministry’s top official in the city. Normally, dozens of trucks make the trip across the bustling and dusty frontier crossing on the tip of North Africa.

An official in Escobar’s office said later it was not clear if more would be allowed to cross into the centuries-old Spanish city of 70,000 nestled between the Mediterranean to the east and northern Morocco to the west.

However, the Spanish newspaper El Mundo quoted protest leader Mounaim Chaouki as saying the blockade would resume Monday, after a break during the Muslim holy day Friday and the weekend, and include construction materials. Today, protesters will prevent Moroccan women who work in Melilla as domestic help from crossing over, Chaouki was quoted as saying.

“The blockade is working,” Chaouki told another newspaper, El Pais. Calls to his cell phone were not answered.

Besides the bustling commercial flow, about 35,000 Moroccans cross daily into Melilla to work or shop.

Morocco claims the city and another North African enclave of Spain, Ceuta, as its own — but Spain rejects any talk of giving up the cities. Many Moroccans enter the enclaves by day to work, then go home at night.

The demonstrators manning the blockade today also were pressing Morocco’s claim to the cities.

Over the past three weeks Morocco has made five complaints alleging Spanish police mistreatment or even racism against Moroccans crossing into Melilla. Moroccan officials also accused the Spanish coast guard of finding, then abandoning, a group of ailing migrants in a boat off the Moroccan coast. Spain has denied any mistreatment.

The Spanish foreign ministry declined comment on the blockade, which started a day after King Juan Carlos called his Moroccan counterpart Mohammed VI to try to ease tensions.

Calls to the Moroccan foreign ministry in Rabat and the Moroccan embassy in Paris went unanswered. The Muslim fasting month of Ramadan began Wednesday.

An official at the Moroccan embassy in Madrid said she had no immediate comment.

Spain and Morocco are key allies, cooperating closely on fighting Islamist terrorism and preventing illegal immigration.

While the blockade could prompt shortages of some products in Melilla if it continues, the people living there won’t starve. Much of Melilla’s food is shipped in from Spain.

Relations are generally good, but periodically suffer from tension. The most serious break came in 2002, when the nations edged close to armed confrontation after a handful of Moroccan troops occupied a rocky Spanish island off the Moroccan coast inhabited by goats. Spain sent warships to the area and ejected the troops. The standoff ended after the United States brokered a deal to remove all forces from the island.

In 2005, another crisis emerged when several thousand destitute African migrants trying to make their way to Europe clambered over razor-wire fences into Melilla and Ceuta over the course of some two weeks.

In their conversation Wednesday, King Juan Carlos phoned Mohammed VI and they reaffirmed the “excellent state of relations” between their countries and promised to work to ensure that “small problems or misunderstandings do not upset this climate,” according to the Spanish royal palace.

The official Moroccan news agency MAP confirmed the call and said the two kings agreed to meet at an unspecified date.