A Spanish mayor has caused anger after posting a mocked-up image of Gibraltar being invaded by Spanish troops and war planes.

Francisco Javier Pérez Trigueros, the mayor of Callosa de Segura municipality in Alicante province, used his Facebook page to distribute an image of a formation of fighter jets trailing red and yellow smoke over Gibraltar as a battalion of saluting Spanish soldiers march in formation with machine guns. A huge cut-out silhouette of a Toro de Osborne bull, an unofficial symbol of Spain, is superimposed on the lower slopes above the 30,000-population British overseas territory.

The image provoked derision on a Gibraltar website where it was posted.

One forum member, Joe Jackson, wrote: "This image reminds me of the Argentines strolling through Port Stanley. It would be a very short and bloody conflict with Spain being the loser."

The provocation comes amid continued tensions between Madrid and London over the future of Gibraltar, which were triggered by a fishing dispute earlier in the summer. Last week divers from GEAS, a specialist diving unit of the Guardia Civil, posed with Spanish flags on the artificial reef deposited in coastal waters by Gibraltar to deter Spanish dragnet fishing.

Inboxes at Gibraltar House, the London office of Gibraltar's government, were jammed with thousands of "abusive" emails written in imperfect English on Tuesday in an apparent campaign of digital harassment aimed at the authorities.

"They said: 'HM government get your people off Spanish soil immediately,' that sort of thing," said Stuart Green, a spokesman for the Gibraltar government.

There were continued delays for residents trying to enter Gibraltar on Monday, as Spanish customs officials continued a go slow, leading to three-hour waits.

Gibraltar's chief minister, Fabian Picardo, flew to London on Tuesday for talks with David Cameron and the foreign secretary, William Hague, about Madrid's "threats" to the territory.

Picardo is hoping to speak to Hague on Wednesday, "Syria permitting", and David Cameron on Thursday, his spokesman said.

"He will talk about the threatening behaviour of Spain, threats of taxes to enter Gibraltar, of making it more difficult for aircraft to land and ill-defined threats by Spain to lift the concrete reef itself," said Green.