WRAPUP 7-Ukrainian general says huge gains made in lightning counteroffensive

(Recasts with context, details)

* Zelenskiy speaks of good news in eastern Ukraine

* Says his forces have recaptured towns and villages

* Ukrainian general says 700 sq kms retaken

* Russian official partially disputes Kyiv's account

* Blinken visits Kyiv with new aid package

By Max Hunder and Pavel Polityuk

KYIV, Sept 8 (Reuters) - Ukraine has recaptured more than 700 sq km (270 sq miles) of its territory in the east and south during a lightning counteroffensive, a Ukrainian general said on Thursday, offering the first official assessment of the operation.

The gains, if confirmed and held, would be a serious blow for Russia, which Western intelligence services say has suffered huge casualties. They would also represent a big boost for Kyiv, which is keen to show its Western backers that it can change the facts on the ground by force and deserves continued support.

Some of the biggest gains appear to have been made this week during a surprise Ukrainian counteroffensive in the Kharkiv region of northeastern Ukraine, which saw Kyiv's forces make a sudden and deep thrust behind Russian lines.

Brigadier General Oleksiy Gromov told a news briefing that Ukrainian forces had advanced up to 50 kilometres (30 miles) behind Russian lines and recaptured more than 20 villages in the Kharkiv region.

He singled out the role of Turkish-made Bayraktar drones.

"Enemy infantry and motorized artillery units unprotected by air defence systems become easy prey for our Bayraktars, the quantity of which is always increasing, thanks to our volunteers," said Gromov.

A Russian official said Moscow's forces had put up stiff resistance and prevented Kyiv's forces from taking at least one key town in the Kharkiv region.

Reuters could not independently confirm the battlefield accounts.

Gromov broke the news as U.S. Secretary of State Antony Blinken arrived in Ukraine. Blinken was expected to announce $2 billion in new foreign military financing to Ukraine and 18 other countries at risk of future Russian aggression. Roughly half the money will go to Kyiv.

U.S. Defense Secretary Lloyd Austin said earlier on Thursday that President Joe Biden had also approved an additional and separate $675 million in weapons to Ukraine as he and other defence ministers met in Germany to discuss how to continue supporting Ukraine in the long-term.

U.S. President Joe Biden was due to hold a call on Thursday with allies and partners to underscore Washington's continued support for Ukraine, the White House said.

The latest announcements of military aid bring the total U.S. security assistance to Ukraine to $15.2 billion since Biden took office in January 2021, a U.S. official said.