Indian travellers vaccinated with two doses of Covishield will still have to undergo 10 days of quarantine in the UK even as the vaccine has been approved under the revised British guidelines for travel, according to UK officials.

They said the main issue is vaccine certification and not the Covishield vaccine and that both India and the UK are holding talks to mutually resolve the matter.

Referring to the latest guidelines issued by the UK government that will come into effect on October 4, the officials said on Wednesday that London does not have any problem with the Covishield vaccine but there are certain issues related to vaccine certification in India.

They said the UK is engaging with the government of India to explore how it could expand its recognition of vaccine certification to people vaccinated by a relevant public health body in India.

Quoting new guidelines, the officials said Indian travellers to the UK must follow the "non-vaccinated rules" set out by the authorities.

India had on Tuesday warned of "reciprocal measures" if the UK does not address its concerns over the new travel rules relating to COVID-19 vaccine certification with Foreign Secretary Harsh Vardhan Shringla describing these norms as "discriminatory".

External Affairs Minister S Jaishankar also took up the issue of Covishield-vaccinated travellers being required to quarantine in the UK with newly-appointed British Foreign Secretary Elizabeth Truss at a meeting in New York on Tuesday.

On Wednesday, the UK government added Covishield, the Indian-manufactured Oxford/AstraZeneca Covid-19 vaccine, to an updated international travel advisory.

"The UK is committed to opening up international travel again as soon as is practicable and this announcement is a further step to enable people to travel more freely again, in a safe and sustainable way, while protecting public health," a spokesperson in the British High Commission said.

"We are engaging with the Government of India to explore how we could expand UK recognition of vaccine certification to people vaccinated by a relevant public health body in India," the official said.