Suspected militants patrolling a road in western Afghanistan shot and killed 14 Shiite Muslim travelers Friday in a rare sectarian attack that Afghans fear is part of an increasing pattern of insurgent assaults on ethnic and religious minorities.

According to the provincial police chief, gunmen stopped two Toyota minibuses in the remote province of Ghowr early Friday, separated Shiite members of the ethnic Hazara community from the other passengers and executed them on the side of the road.

Four members of the same family — a newly engaged couple and two of their relatives — were killed in the attack. The assailants bound some of the victims’ hands and blindfolded others before they were shot, security officials told Afghanistan’s TOLO News agency.

Afghan officials blamed the massacre on Sunni Taliban insurgents, who are battling Afghan and foreign troops. But the group did not assert responsibility for the attack.

“The Taliban wants to divide Afghans along ethnic and sectarian lines,” said Sayed Nader Shah Bahr, a parliament member from Ghowr.

Ghowr is an isolated and mountainous region wedged between Hazara-majority Bamian province in the east and Herat province in the west, on the Iranian border. Ethnic Hazaras, the majority of whom are Shiite Muslims, make up a sizable portion of Ghowr’s population of about 580,000, according to Afghan government statistics. Nationwide, they are believed to constitute about 10 percent of the population, but authorities have not conducted a credible census here in decades.

When the Taliban ruled Afghanistan from 1996 to 2001, its forces carried out sectarian killings of the Hazara population. The Taliban, which subscribes to an austere form of Sunni Islam, says adherents of the Shiite sect are infidels, or nonbelievers. Shiite Muslims believe that the son-in-law of the Muslim prophet Muhammad — rather than one of his closest companions — was the rightful heir of the Islamic caliphate. The split goes back to the beginning of Islam in the 7th century.

Despite the rifts and ongoing Taliban insurgency, Afghanistan has largely been spared the type of sectarian bloodshed that has cleaved its neighbor Pakistan in the years following the fall of the Taliban in 2001.

The first major assault in the post-2001 period came in December 2011, when a suicide bomber blew himself up in the midst of the Shiite festival of Ashura in Kabul, killing more than 60 people. The Pakistani Sunni militant group Lashkar-e-Jhangvi claimed responsibility for the attack, which shocked Afghanistan and raised fears that the years-long insurgency here could deteriorate further into a full-blown sectarian conflict.

The execution-style slayings Friday took place on a highway outside the Ghowr provincial capital, Firoz Koh, near the village of Bagah.

Ghowr’s governor, Sayed Ahmad Rahmati, told the Persian-language service of the BBC that a local Taliban cell had killed the travelers — who were coming back to the province from a shopping trip in the capital, Kabul — after failing to make gains against security forces in Ghowr in the past several weeks.

“They wanted to show their presence” in the province, Rahmati said in the interview.

In another development Friday, the Associated Press reported that Tabiban leader Mohammad Omar warned that fighting would continue if the next president of Afghanistan signs a bilateral security agreement with the United States that allows thousands of American troops to stay in the country. Both candidates for president, now engaged in a dispute over election results, have said they would sign such an agreement.

The White House said President Obama spoke by telephone Friday with the candidates, Ashraf Ghani, the apparent front-runner, and Abdullah Abdullah, to urge them “to continue to move forward in the spirit of collegiality” to resolve their differences.

Mohammad Sharif in Kabul and Karen DeYoung in Washington contributed to this report.