ISLAMABAD — Three bomb blasts tore through a Shiite Muslim procession Wednesday in Pakistan’s second-largest city, Lahore, killing at least 28 people and wounding 200 others, authorities said.

The attacks occurred as thousands of Shiites marched through Lahore’s streets in a traditional mourning procession for Yaum-i-Ali, one of Shiite Islam’s most revered holy figures. No one claimed responsibility for the blasts, but Sunni Muslim militant groups have frequently targeted Pakistan’s Shiite minority in the past.

Lahore’s top administrative official, Khusro Pervez, called the attacks “”very well planned”” and carried out at a time when Pakistani authorities have been preoccupied with massive floods that ravaged large sections of the country this summer.

The blasts began just after Iftar, the early evening period when Muslims break their daily fast during the holy month of Ramadan. The first explosion was a low-intensity blast that struck marchers as they neared the procession’s endpoint. A television camera showed frantic marchers crawling from the site amid a cloud of black smoke.

Minutes later, two other explosions that authorities said were suicide bombings occurred at a gate about 300 yards from the first blast. Those explosions resulted in most of the deaths and injuries.

Akhtar Ali, an official with the Edhi rescue service, said the death toll stood at 28 as of late Wednesday evening, but he added several of the injured were in critical condition and said the death toll likely could rise.

After the blasts, police struggled to maintain order as angry Shiites set ablaze a police station and three police cars. Television footage also showed stick-wielding marchers clubbing fleeing police officers.

Lahore is the capital of Punjab, Pakistan’s wealthiest and largest province, which remains rife with violent sectarian groups that prey on religious minorities, including Shiites, Christians and members of the minority Ahmadi sect. Those groups have been banned by the government for years, but their organizations historically have been permitted to operate freely throughout Punjab province.