"This is a really significant deal, because it's pound8 billion ($10.7 billion) worth of orders... These are jobs that will last for 10 years, making the (Eurofighter) Typhoons, so really big for our country," Starmer said.

Britain's defence ministry described the order, which involves 20 Eurofighter Typhoon planes, as the "biggest fighter jet deal in a generation", saying it would strengthen Turkey's combat capabilities and bolster "NATO's strength in a key region".

Starmer said the deal would "bolster security across NATO" and secure 20,000 British jobs, adding it included the option to supply more Eurofighters in the future.

Erdogan hailed the agreement as "a new symbol of the strategic relations" with Britain, and thanked the other members of the four-nation consortium that builds the jets: Germany, Italy and Spain.

British defence minister John Healey, who travelled to Ankara with Starmer, said the deal "goes far beyond" aircraft.

"It is the leading edge of the growing defence and industrial partnership between our two nations," he said, calling Turkey "an important NATO ally and the gatekeeper to the Black Sea".

- Spying scandal -

But the high-profile visit was clouded by a spying scandal that erupted late on Sunday, after a Turkish court charged Istanbul's jailed opposition mayor with espionage over his links to a Turkish businessman allegedly spying for Britain.

Neither side commented on the affair, which dominated the headlines in Turkey on Monday morning.

Starmer arrived with Healey and Air Chief Marshal Harv Smyth, the head of Britain's air force, who were welcomed by their Turkish counterparts, Turkey's defence ministry said.

As part of Starmer's visit, three Eurofighter jets of the Royal Air Force also arrived in Turkey, the ministry added.

Apart from those three jets escorted to an air base near Ankara, two more Eurofighter jets also arrived in Turkey, a Turkish security source told AFP, speaking on condition of anonymity because he was not authorised to speak to the press.

It was not immediately clear whether the two jets would be handed over to Turkey or would be used for the training of Turkish pilots.

Ankara has been looking to modernise its air force and is pushing to acquire 40 of the European-made fighter aircraft.

Negotiations with London gained pace after Germany in July lifted its veto on the sale over Ankara's hardline stance on the Gaza war.

"Turkey and the Eurofighter is quite the saga," Aaron Stein, head of the Foreign Policy Research Institute, told AFP, saying Ankara had turned down an offer to join the European consortium building the jets, focusing instead on the US F-35 fighter jet programme.

After Washington booted Ankara out of its F-35 programme in 2019 over its purchase of an S-400 Russian surface-to-air missile defence system, Turkey turned its attention to Europe.

- Qatari leader's visit -

Last week, Erdogan held talks in Doha with Qatar's Emir Sheikh Tamim bin Hamad Al Thani, with Turkey floating plans to acquire some of the emirate's Eurofighters.

Qatar ordered 24 Eurofighters in 2017, with the last two due to be delivered this year. It moved to acquire 12 more late last year, observers said.

Any such move would likely be part of the deal with London, which would have to grant its approval for a transfer, analysts said.

The Qatari leader is in Ankara on Tuesday for talks to clarify certain outstanding issues, the Turkish official said.

The Eurofighter jets delivered to Turkey on Monday were likely to be those that had been destined for Qatar, Stein said.

Instead of being sent to Doha, "they'll simply be shipped to Turkey," he explained.

Gaza's future was also likely to feature in talks between Erdogan and Starmer, with Turkey keen to join an international stabilisation force -- an idea opposed by Israel.