BEIJING — Two men rammed a truck into a group of jogging policemen and tossed explosives, killing 16 officers today in an attack in a restive province of western China just days before the Beijing Olympics, the state-run Xinhua News Agency reported.

Though it happened on the far side of the country — near the Afghan-Pakistan border — the attack came as security forces were on alert for the Games, which open Friday. It was among the deadliest and most brazen attacks in years in Xinjiang province, site of a sporadically violent rebellion by local Muslims against Chinese rule.

About 20 people upset at having been evicted from their homes staged a brief demonstration near Tiananmen Square, Beijing’s heavily guarded political center. Uniformed police quickly surrounded the group until members of a neighborhood committee came and pulled the protesters away, scuffling with some.

In the Xinjiang attack, the two men drove a dump truck into the group of border patrol police officers as they passed the Yiquan Hotel during a routine 8 a.m. jog in the city of Kashgar, the Xinhua News Agency reported.

After the truck hit an electrical pole, the pair jumped out, ignited homemade explosives and “also hacked the policemen with knives,” Xinhua said.

Fourteen died on the spot and two others en route to a hospital, and at least 16 officers were wounded, Xinhua said.

Police arrested the two attackers, one of whom was injured in the leg, the report said.

Authorities closed off streets, sealed the Nationalities Hospital down the street from the explosion, and ordered people to stay inside, said a man answering phones at the hospital duty office.

Local government officials declined comment today. An officer in the district police department said an investigation was launched.

Kashgar, or Kashi in Chinese, is a tourist city that was once an oasis trading center on the Silk Road caravan routes and lies 80 miles from the border with Pakistan, Afghanistan and Kyrgyzstan.

Chinese security forces have been on edge for months, citing a number of foiled plots by Muslim separatists and a series of bombings around China in the run-up to the Olympics. Last week, a senior military commander said radical Muslims who are fighting for what they call an independent East Turkistan in Xinjiang posed the single greatest threat to the games.

A spokesman for Beijing’s Olympic organizing committee said he did not have enough information to comment on the bombings. But he said security arrangements were being increased around the Olympic venues.

“We’ve made preparations for all possible threats,” the spokesman, Sun Weide, told reporters. “We believe, with the support of the government, with the help of the international community, we have the confidence and the ability to host a safe and secure Olympic Games.”

A Chinese counterterrorism expert, Li Wei of the China Institute for Contemporary International Relations in Beijing, said the attack was likely the work of local sympathizers, rather than trained terrorists who sneaked across the border into China.

Xinhua said that Xinjiang’s police department earlier received intelligence reports about possible terrorist attacks between Aug. 1 and 8 by the East Turkistan Islamic Movement. The movement is the name of a group that China and the U.S. say is a terrorist organization, but Chinese authorities often use the label for a broad number of violent separatist groups.

In Xinjiang, a local Turkic Muslim people, the Uighurs (WEE’-gurs), have chafed under Chinese rule, fully imposed after the communists took power nearly 60 years ago. Occasionally violent attacks in the 1990s brought an intense response from Beijing, which has stationed crack paramilitary units in the area and clamped down on unregistered mosques and religious schools that officials said were inciting militant action.

Uighurs have complained that the suppression has aggravated tensions in Xinjiang, making Uighurs feel even more threatened by an influx of Chinese and driving some to flee to Pakistan and other areas where they then have readier access to extremist ideologies.

One militant group, the Turkistan Islamic Party, pledged in a video that surfacmed on the Internet last month to “target the most critical points related to the Olympics.” The group is believed to be based across the border in Pakistan, with some of its core members having received training from al-Qaida and the Pakistani Taliban, according to terrorism experts.

Terrorism analysts and Chinese authorities, however, have said that with more than 100,000 soldiers and police guarding Beijing and other Olympic co-host cities, terrorists were more likely to attack less-protected areas.