Trinamool Congress chief Mamta Banerjee was on Thursday night put under "close observation" following detection of a blood clot in her chest, sources at the nursing home where she is admitted said.

"Evidence of bleeding was detected in the area of chest. Thereafter, she was referred to specialists who have advised for her to be kept under close observation," sources said.

Banerjee was admitted to the nursing home early on Thursday following her complaints of chest pain and breathing difficulty.

Party general secretary Mukul Roy said the Trinamool Congress chief felt unwell while attending a joint rally with Congress on Wednesday to protest the police lathicharge during a Trinamool dharna led by her on Monday night at Singur in Hooghly district against land acquisition for the Tata Motors [Get Quote] car project.

Roy said Bharatiya Janata Party chief Rajnath Singh telephoned him to enquire about Banerjee's condition.

The BJP leader also expressed his party's support to her agitation in West Bengal. The TC is still officially the ally of BJP.

On Wednesday, Rajnath Singh had described her an 'icon of people's struggle' in West Bengal and condemned the police action on her dharna.