Several Chinese runners were not far from the finish line of the Boston Marathon on Monday when two deadly blasts turned excitement and cheers into confusion.

"I heard the explosion and saw the smoke near the finish line and shortly, within seconds, another one went off about 100 meters away," recalled Zhu Wenming, who ran the marathon with a team from Chinese real estate developer Vanke Co.

Two women walk from the area where a bomb exploded during the Boston Marathon on Monday, killing at least three and wounding more than 170. [Photo/Agencies]

The two blasts killed at least three people, including an 8-year-old child, and injured at least 170, many critically.

Zhu heard the first explosion about two minutes after he crossed the finish line.

"A woman near me immediately kneeled down and started crying. It was a bit chaotic," the 31-year-old added.

Police had not identified any suspects by press time.

Monday's Boston Marathon attracted some 27,000 runners from around the world - including a group of 15 from Vanke.

As they were getting ready for the race in the morning, Vanke runners - none of whom are professional marathon runners - told China Daily they wanted to challenge themselves by participating.

The Shenzhen-based residential developer was also one of the sponsors of this year's marathon.

"I wasn't aware of what happened when the first explosion occurred, and I realized it was a planned incident after the second one went off," said Wang Shi, chairman of Vanke, who led the team to the Boston Marathon.

Wang, who sat in the VIP box across the street from the explosions, described the "calm and good order" as police were evacuating spectators - reported to number around 500,000.

"Only when we returned to the hotel and watched the TV did we see how serious the situation was," said Wang, adding he was relieved to see everyone in his group was OK.

Among the 15 Vanke runners, seven of them made it to the finish line before the explosions happened.