Istanbul (AFP) - Turkish security forces have over the last three days detained 45 foreign nationals seeking to cross into Syria to join Islamic State jihadists from the southeastern city of Gaziantep, the Dogan news agency reported Sunday.

If confirmed, the detentions would mark a stepping up of pressure on IS by the Turkish authorities after the arrest of 21 suspected members of the group in Istanbul and elsewhere on Friday.

Gaziantep has long been seen as a staging post for IS recruits who travel to the city by bus after flying from their countries to Istanbul. They then make the short illegal journey over the border to Syria.

Dogan news agency said that on Sunday alone, 25 foreign nationals, mainly citizens of Tajikistan, had been arrested at Gaziantep bus station.

It said that police units had been working intensively at the bus station since Friday and had in total detained 45 people who wanted to cross into Syria to join IS.

Many would-be jihadists had also brought their families with them, it added.

The suspects have undergone health checks and are being interrogated, after which they will likely be deported.

In a separate operation, Turkey had on Friday detained 21 suspected members of IS, of whom three were foreigners, in several cities including Istanbul, state media said.

Western states have repeatedly accused Turkey of not doing enough to halt the flow of jihadists across its 911-kilometre (566-mile) border with Syria.

Turkey fiercely rejects the accusations, saying it is making every effort to secure a long border. In turn, it has accused the West of not playing its part to shoulder the burden of hosting 1.8 million refugees from Syria.

In an apparent bid to deflect criticism, Turkish authorities have arrested a number of suspected militants in recent months.

The latest arrests came after a two-day visit this week by a senior US delegation during which Turkey pledged more cooperation in the fight against IS jihadists in Syria.