Beijing, Aug 26 (IANS): Tinku Lukka's best performance of the season was not enough to earn a semi-final spot as the Indian runner finished seventh in her heat to crash out of the women's 800 metres competition at the World Athletics Championships here on Wednesday.

The Kerala athlete, who is coached by the legendary P.T. Usha, recorded a time of two minutes and 0.95 seconds to finish seventh out of eight competitors in Heat 1 at the Bird's Nest Stadium.

Marina Arzamasova of Belarus won the heat with a time of 1:58.69. She registered the fastest first-round time in the history of the championships.

Out of 45 athletes who featured in the heats, 24 qualified for the semis. Apart from the three winners in each of the six heats, the next six best performers also went through.

Tintu -- who recorded her personal best of 1:59.17 in Spilt, Croatia, in 2010 -- clocked 57.06 seconds to lead the first 400m.

But the reigning Asian champion, who is yet to go below two minutes this season, lost the plot in the second round as she was not able to accelerate towards the end.

Defending champion Eunice Jepkoech Sum of Kenya (1:59.67) eased to victory in the second heat to also qualify for the next stage.

Lalita Babar is the only other Indian in action here on Wednesday. She will take part in the women's 3,000m steeplechase final later in the day.