GAZA, May 23 (Reuters) - Three months into the Russian invasion of Ukraine, which has closed off access to lower-priced Black Sea wheat, owners of five mills in the Palestinian Gaza Strip are feeling the heat as they try to replenish stocks.

Prices have jumped by around 20%, meaning the territory's five mills are struggling to compete with imported stock sold at slightly cheaper rates from Egypt and the West Bank, which have lower production costs than Gaza.

"Our capacity stood at 400 tonnes of wheat a day or 300 tonnes of flour... Nowadays, it has fallen to (just) 10 to 20% of that," he told Reuters at the facility in southern Gaza, where most of the machines were switched off.

"The main reason is the Russian-Ukraine war. We had stores for two to three months, but when they ran out we were obliged to buy wheat at new prices, and it was very high," he told Reuters.