A 35-year-old man died in Sunday's Movistar Madrid Half Marathon after collapsing due to cardiac arrest in the final straight. Another 20-year-old participant also suffered from cardiac arrest and remains in intensive care.

The former is understood to have been just 500 metres from the finish line on Paseo de Recoletos when he fell ill. Spanish news sources quoted a source from Emergencies Madrid, which said he was transported to La Paz hospital "without a pulse" and later died. According to reports, a nurse from Samur-Protección Civil at Cibeles attended to the 35-year-old at the scene in an unsuccessful attempt to revive him. Organisers behind the half marathon expressed their "deepest condolences" but did not provide more details on the deceased, with only three weeks to go before the London Marathon is held.

The 20-year-old male was also attended to on Paseo de Recoletos by a doctor who was spectating and two members of security. It's understood he was resuscitated at the scene before being taken into intensive care at Hospital Clínico.

As of Monday afternoon, it's understood the younger runner's condition remains unknown. This news comes despite organisers' efforts to limit the strain of Sunday's race by moving the finish line.

The Madrid Half Marathon formerly ended at El Retiro Park, which is located at the end of one final incline that served as one final challenge for participants. However, the finish was moved to Paseo de Recoletos, outside the National Library, after a 31-year-old died in 2010 once they crossed the line.

Another man also died in 2005 midway through the 20-kilometre test. The 24-year-old also went into cardiac arrest, a case that was so bad medical staff "could do nothing to save his life."

A total of 27,000 people are believed to have taken part in Sunday's half marathon, which was first held in 2001. And medical professionals were kept busy attending to other, more minor cases.

It's reported around 50 people were treated for ailments like heat stroke and sprains in Madrid on Sunday. The weather in Spain's capital this weekend was fairly mild with peaks of 18 degrees, though humidity levels were as high as 100% in the morning, per the Met Office.