The 25-year old has been in excellent form coming off the back of a title winning season with Rangers.
His displays for Finland against Denmark and Russia have earned rave reviews as he strives to push his country through their group but they face a stern test on Monday against Belgium.
Kamara is a firm favourite with his manager Steven Gerrard but Rangers have yet to tie him down to a new contract and the former Arsenal junior has just 12 months remaining on his current deal, reports the Daily Mail.
Watford are looking to add a defensive midfielder and Kamara is a player they have discussed extensively.
They have yet to make a bid and know Rangers would be reluctant to sell cheaply but Kamara's performances are attracting rival interest.